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AMERICAN SCIENCE SERIES, ELEMENTARY COURSE 



THE ELEMENTS 



OF 



CHEMISTRY 



A TEXT-BOOK FOR BEGINNERS 



BY 

IKA REMSEN" 

Professor of Chemistry in the Johns Hopkins University 




NEW YORK 
HEKRY HOLT AND COMPANY 

1900. 



<$*. 



Copyright 1886, 

BY 

HENRY HOLT & CO, 



48 6555 

JUL 2 4 1942 






K i 



ROBERT DRUMMOND, PRINTER, NEW YORK. 



PREFACE. 



This book is written upon much the same plan as the 
Briefer Course in the same series. It is, however, mate- 
rially simpler in many parts, and is in every way better 
adapted to younger pupils. In the opinion of the author 
a rational course in chemistry, whether for younger or older 
pupils, is something more than a lot of statements of facts 
of more or less importance; a lot of experiments of more 
or less beauty; or a lot of rules devised for the purpose of 
enabling the pupil to tell what things are made of. If the 
course does not to some extent help the pupil to think as 
well as to see, to reason as well as to observe, it does not 
deserve to be called rational. Not only must the pupil 
perform experiments, but he must know why he performs 
them, and what they teach. A good plan to follow is to 
talk over a certain part of the subject, showing how to con- 
struct the apparatus necessary for some of the experiments, 
and stating in a general way what is to be learned; then to let 
the pupil perform the experiments with the aid of the book 
and the teacher; and afterwards to make the experiments 
the basis for questioning. In this way the pupil will be- 
come observant, and at the same time he will discover when 
his experiments have been performed in the wrong way. 
It is better to go slowly at first so as to allow the pupil 
time to become familiar with his surroundings and to enable 



IV PREFACE. 

him to learn how to work at the laboratory desk. A badly 
constructed piece of apparatus or an experiment badly per- 
formed in any way should not be allowed to pass. Experi- 
ments should be repeated as many times as may be neces- 
sary to secure accurate work. 

Chemical theories are treated in a subordinate way, as it 
is believed that the attention should first be directed to the 
simpler facts of the subject and the methods by which these 
facts are learned. A brief statement of a few of the pre- 
vailing hypotheses is given in Chapter XIV. Whether it 
will be advisable for the pupils to spend any time in study- 
ing this chapter will depend upon their age and their men- 
tal attainments. If all they can do is to learn the statements 
by heart and repeat them without showing any signs of 
comprehension, then unquestionably the chapter should be 
omitted. It should be remembered that the object of the 
course laid down in this book is not to make chemists, but 
to help to develop sound minds, and at the same time to 
awaken interest in a set of natural phenomena of great im- 
portance to mankind. It is quite possible to teach the sub- 
ject in such a way as to destroy all interest in chemical 
phenomena and to make the pupil shudder whenever a chemi- 
cal formula is mentioned. There is no better way to accom- 
plish the latter result than by giving prominence to incom- 
prehensible theories and forcing the pupils to master a lot 
of equations which represent facts of which they are entirely 
ignorant. 

Baltimore, December 27, 1886. 



CONTENTS. 



CHAPTER I. 

PAGE 

Chemical Changes— Physical Changes ...... . . 1 

CHAPTER II. 
The Chemistry of the Air 16 

CHAPTER III. 
Oxygen c . . . &1 

CHAPTER IV. 
Combining Weights 31 

CHAPTER V. 
Nitrogen 37 

CHAPTER VI. 
Water 41 

CHAPTER VII. 
Hydrogen 45 

CHAPTER VIII. 
Water (continued) 53 

CHAPTER IX. 

Compounds of Nitrogen with Hydrogen and Oxygen .... 66 

CHAPTER X. 

Chlorine and Its Compounds with Hydrogen and Oxygen. . . 77 



VI CONTENTS. 

CHAPTER XL 

PAGE 

Acids—Bases — Neutralization— Salts 88 

CHAPTER XII. 
Carbon 95 

CHAPTER XIII. 

Compounds of Carbon with Hydrogen, with Oxygen, and with 

Nitrogen 106 

CHAPTER XIV. 

Atomic Theory— Atomic Weights— Molecular Weights— Valence 

— Classification of the Elements 124 

CHAPTER XV. 
The Chlorine Family: Chlorine, Bromine, Iodine, Fluorine. . 132 

CHAPTER XVI. 
The Sulphur Family: Sulphur, Selenium, Tellurium .... 139 

CHAPTER XVII. 

The Nitrogen Family: Nitrogen, Phosphorus, Arsenic, and Anti- 
mony—Boron and Silicon 15! 



' 



CHAPTER XVIII. 
Base-forming Elements — General Considerations 161 

CHAPTER XIX. 
The Potassium Family: Potassium, Sodium, (Ammonium) . . 165 

CHAPTER XX. 

The Calcium Family: Calcium, Barium, Strontium < . . 178 

CHAPTER XXI. 

The Magnesium Family: Magnesium, Zinc, Cadmium— The 

Copper Family: Copper, Mercury, Silver 185 



CONTENTS. VH 

CHAPTER XXII. 

PAGE 

The Aluminium Family — The Iron Family: Iron, Cobalt, 

Nickel 196 

CHAPTER XXIII. 
Manganese— Chromium— Uranium — Bismuth 206 

CHAPTER XXIV. 
Lead—Tin— Platinum— Gold 209 

CHAPTER XXV. 
Some Familiar Compounds of Carbon 216 

CHAPTER XXVI. 
Other Compounds of Carbon 231 



APPAKATUS AND CHEMICALS. 

For the benefit of those who have no laboratory at 
command, and who may wish to make arrangements for 
going through with the experimental work, the following 
list has been drawn up. In it is included everything 
necessary to perform the experiments on a small scale. 
Should it be desired to fit up a room with conveniences for 
students, the amount of apparatus necessary would depend 
upon the number of students, but for each individual the 
expense would be small, as many of the pieces of apparatus, 
such as the galvanic battery, burette, weights, scales, etc., 
need not be multiplied. In place of some of the pieces of 
apparatus described in the book, ordinary kitchen utensils 
will answer: thus, for example, instead of the trough for 
collecting gases, a tin pan or a deep earthenware dish may 
be used; instead of the water-bath, a stew-pan, fitted with 
two or three different-sized tin or sheet-iron rings; and in 
place of glass cylinders for working with gases, wide- 
mouthed cheap bottles. 

The publishers do not deal in chemicals and apparatus, 
nor, they may as well say, receive commissions on them. 
Any orders should be sent direct to the dealers. 

Messrs. Eimer & Amend, Nos. 205 to 211 Third Avenue, 
New York, whom the publishers take the responsibility of 
recommending as thoroughly reliable, will furnish each of 
the following articles at the price given. 

If several pieces of the apparatus in List No. 1 are taken, 
a discount of 10 per cent will be made; on a complete set 
20 per cent discount will be allowed; on three or more sets, 
25 per cent. 

One or more of the articles in List No. 2, if not marked 
"net" or "20 per cent," will be supplied at 25 per cent 
discount if ordered with sets of the apparatus in List No. 1. 

A discount of 10 per cent will be given on a complete 
set of the chemicals, and of 15 per cent on three or more 
sets. 






APPABATUB AJ3D CEBM1CALS. 



IX 



For most items less than the whole set, there will have 
to be a small additional charge for packing. It should be 
realized, however, that usually the charge for packing one 
article must be as large as for several. Some articles can, 
of course, be mailed without any charge for packing. 



List No. 1. 



A list of apparatus and chemicals necessary for performing all of 
uhe experiments in Remsen's Elements of Chemistry, with the excep- 
tion of experiments Nbs. 34, 36, 
113. To perform ther~ 
List No. 2 is required. 



A list ol apparatus and chemicals u 
the experiments in Remsen's Elements oi ^ut 
tion of experiments Nbs. 34, 36, 46, 47, 48, 49, 51, 65, 66, 79, 80, and 
113. To perform these latter experiments, the apparatus given in 



APPARATUS. 

1 Nest Beakers, 1-3 $0 40 

1 Jeweller's Blowpipe, 8 in 15 

7 Wide-mouth Flint Bottles, two 

each, 2, 4, 8 oz., and one 32 oz. 50 
1 Bunsen's Burner with regula- 
tor, or 6 oz. glass alcohol 

lamp, same price 50 

1 5-in. U-tube 25 

2 doz. Assorted Corks 20 

1 Nest Hessian Crucibles, 

"threes" ... 6 

1 1^4 -in. Porcelain Crucible 18 

1 25 CC Grad. Cylinder 50 

1 Deflagrating Spoon 25 

1 each Evaporating Dish, 23^ 

and 3^ in 40 

1 Lead Dish, 2 in 25 

1 Round File, 5 in 25 

1 Triangular File, 5 in 25 

1 Pack White Filters, 4 in ....... . 12 

4 Flasks: one 4 oz., two 8 oz., 

oriel6oz 80 

1 SteelForceps 20 

2 Funnels, 2^ in 24 

2 Funnel Tubes, one 10 in. , one 

15 in . . 35 

1 Gas Bottle, 8 oz., with 2-hole R 

Stopper 40 

*4 lb. Assorted Glass Tubing, 4-7 15 

2 Sheets each Red and Blue Lit- 

mus-paper 20 

1 Horseshoe Magnet, 3 in 20 

1 Porcelain Mortar and Pestle, 

3^ in 45 

1 Piece Platinum Foil, lxl ^ in. . 60 

6 in. Medium Platinum Wire 20 

1 Plain Retort, 8 oz 30 

1 Stoppered Retort, 16 oz 55 

3 ft. Rubber Tubing for gas, ^ in. 39 
(Only needed if Bunsen's Burner 

is used.) 

2 ft. Rubber Tubing (for connec- 

tions) 20 



1 %\i in. Sand Bath $0 15 

1 Hand Scale, with weights 85 

1 Test Tube Stand 30 

12 Test Tubes, 5 in 30 

1 Test Tube Brush 5 

1 Test Tube Clamp 20 

1 Iron Tripod 30 

2 2-in. Watch-glasses 10 

1 5-in. Water-bath. 1 00 

2 Wire Clamp Supports 2 00 

$14 74 
CHEMICALS. 

4 oz. Acid Acetic, pure (bottle 5 

cents extra) $0 10 

4 oz. Acid Arsenious ... 10 

16 oz. " Hydrochloric (bottle 

15 cents extra). 10 

8 oz. Acid Nitric (bottle 12 cents 

extra) 10 

2 oz. Acid Oxalic 10 

16 oz. " Sulphuric (bottle 12 

cents extra) 10 

1 oz. Acid Tartaric 10 

2 oz Alcohol, for experiments 

only (bottle 4 cents extra). . . 10 

8 oz. Alum 10 

4 oz. Ammon. Chloride 10 

8 oz. " Hydrate, concen- 
trated (bottle 10 cents extra) 10 

4 oz. Ammon. Nitrate ... 10 

2 oz. Antimony, powdered 10 

2 oz " and Potassium 

Tartrate 20 

2 oz. Barium Chloride 10 

4 oz. Calcium Chloride, fused. .. 10 

4 oz. " Sulphate 10 

4 oz. Carbon Disulphide (bottle 

5 cents extra) 10 

8 oz. Animal Charcoal, powdered 10 

8 oz. Copper Foil 30 

4 oz. k * Sulphate 10 

1 oz. " Oxide... 15 

4 oz. Fluorspar, powdered 10 



APPARATUS AND CHEMICALS. 



1 oz. Indigo. $0 10 

1 oz. Iodine (bottle 2 cents ex- 

tra) 40 

4 oz. Iron Filings, fine ,.. 10 

8 oz. " Sulphide 10 

4 oz. " Sulphate 10 

4 oz. Lead Sheet 10 

4 oz. " Acetate 10 

2 oz. " Nitrate 10 

1 oz. " Peroxide 10 

2 oz. " Sesquioxide 10 

1 oz. Litmus 10 

^ dram Magnesium Ribbon 20 

1 lb. Manganese Dioxide, pow- 
dered 10 

1 oz. Mercury Red Oxide ]0 

1 oz. Nutgalls, powered 10 

2 oz. Parafflne 10 

1 oz. Phosphorus (hot. 10c. extra) 15 

1 dram Potassium ... 50 

2 oz. " Bromide 10 

4 oz. " Carbon, (bot. 

5 cents extra) 10 



4 oz. Potassium Chlorate $0 10 

4 oz. " Dichromate 10 

2 oz. " Ferrocyanide .. 10 
4 oz. " Hydrate Sticks 

(bottle 5 cents extra) 20 

1 oz. Potassium Iodide (bottle 5 

cents extra) 30 

4 oz. Potassium Nitrate 10 

2 oz. *' Permanganate. 10 

1 dram Sodium (bot. 3c. extra). . 10 

2 oz. ** Acetate 10 

2 oz. " Bicarbonate..... 10 

4 oz. " Biborate (Borax) 10 
4 oz. * 4 Hydrate (bottle 

5 cents extra) 20 

4 oz. Sodium Nitrate 10 

4 oz. " Sulphate 10 

8 oz. Sulphur, roll 10 

4 oz. Tin, granulated 10 

16 oz. Zinc, granulated...., 30 

2 oz. " Sulphate 10 

$8 00 



List No. 2. 

In order to perform experiments Nos. 34, 36, 46, 47, 48, 49, 51, 65, 
66, 79, 80, and 113, the following additional apparatus is necessary: 



2 Qt. Bunsen's Cells $3 00 

2 Platinum Plates, lx^ inch 40 

1 Charcoal Furnace,18in.(20p.c), 2 00 

or 1 Charcoal Furnace, 24 in., 

$3 00(20p.c.);orl 10 burnerGas 

Combustion Furnace $20 00 

1 25-in. hard Glass Tube, 1 in. bore 

(net) 1 00 

or 1 25-in. Porcelain Combus- 
tion Tube, 1 in. bore.. ..$1 75 

3 pt. Woulff's Bottles, 2-necked. . 1 95 
1 hard Glass Tube, drawn out, 

12x^jin. bore 25 



1 Oxyhydrogen Blowpipe $6 00 

2 Gasholders for Oxygen and Hy- 

drogen, 5 gal 26 50 

1 Liebig's Condenser, 15 in 1 50 

1 Burette, 50 c.c. f 1 70 

1 Pinchcock 25 

1 Copper Air-bath, 6x8 in 5 00 

1 Kellog-Bunsen's Vapor Lamp, 
complete (a substitute in case 
gas is not used as fuel) (net).. 10 00 

$59 55 



THE ELEMENTS OF CHEMISTRY. 



CHAPTER I. 
CHEMICAL CHANGES— PHYSICAL CHANGES. 

Some Familiar Changes. — You are all familiar with 
many changes which are taking place in the things around 
you. Take, for example, the changes which are called 
fire. You see substances destroyed by fire. They disap- 
pear. You feel the heat produced by the burning. You 
know that some things will burn and others will not. 
Again, you all know that iron when exposed to the air is 
changed, becoming covered with a reddish-brown substance 
called rust. If fruit- juices or milk be allowed to stand in 
contact with the air they become sour. If a spark comes 
in contact with gunpowder there is a flash and the powder 
disappears, dense smoke appearing in its place. 

Changes of Another Kind. — If a piece of stone or of iron 
be brought in contact with something hot it becomes hot 
itself. If taken away it becomes cool again. If heated 
very hot it gives light. When, for example, iron becomes 
" red-hot" we can see it in a dark room. Iron may also 
be changed by contact with loadstone. After it has been 
rubbed with loadstone it has the power to attract and hold 
to itself other pieces of iron. When a solid body is struck 



2 THE ELEMENTS OF CHEMISTRY. 

with another solid a sound is produced. At a low temper- 
ature water is solid, forming ice. If the ice becomes warm 
enough, it melts and becomes water. If the water is 
heated enough it becomes steam. By cooling steam it 
changes to water, and by cooling water it changes to ice. 

Two Kinds of Change. — When a substance burns it be- 
comes something entirely different. Iron-rust is not iron. 
Sour milk is not fresh milk. Gunpowder after the flash 
is not gunpowder. In these cases, then, the substances 
which are changed disappear and something else is formed 
in their place. On the other hand, when a piece of iron 
which is hot is allowed to cool it is the same thing that it 
was before it was heated. Eed-hot iron soon ceases to 
give light if it is taken away from the fire. Water may 
be cooled down and changed to ice, and the ice heated and 
changed to water; and the water formed from the ice is 
exactly the same thing as the water from which the ice 
was formed. In these cases the substances are not per- 
manently changed. You see thus that we have two classes 
of changes presented to us for study: 

1st. Those which do not affect the composition of sub- 
stances. 

2d. Those which affect the composition of substances 
and give rise to the formation of new substances with 
new properties. 

Changes of the first kind are called physical changes. 
Those of the second kind are called chemical changes. 

Physics and Chemistry. — That branch of knowledge which 
has to deal with physical changes is known as physics f 
and that which has to deal with chemical changes is 
known as chemistry. Everything that has to do with 
motion, with heat, light, sound, electricity, and magnet- 



CHEMICAL CHANGES— PHYSICAL CHANGES, 3 

ism, is studied under the head of Physics. Everything 
that has to do with the composition of substances and 
changes in the composition is studied under the head of 
Chemistry. 

All Physical and Chemical Changes are Related. — Al- 
though at first sight the different kinds of change already 
mentioned appear to be quite distinct from one another, 
they are in reality closely related. If a body in motion be 
stopped suddenly it becomes hot. Many examples of a 
similar change of motion into heat are familiar : a wire 
becomes hot when hammered on an anvil ; a coin rubbed 
on cloth becomes hot. In both cases the cause of the heat 
is the interference with the motion. The hammer is 
stopped and becomes hot ; the coin is not stopped, but the 
motion is interfered with, and we have to push harder in 
order to move it over the cloth than we should to move it 
in the air. Again, we know that by means of heat we can 
produce motion. The steam-engine is the best example of 
this. We build a fire ; this heats the water in the boiler ; 
the water is converted into steam, which expands and 
moves the piston, and the motion of the piston is the seat 
of all the complex motions which are found in the different 
parts of the engine. The train or ship moves. What 
moves it ? Plainly, the heat is the cause of the motion. 
But we can go a step farther back and ask what causes the 
heat. The answer is clear. It is the burning of the fuel. 
But, in burning, the composition of the fuel is completely 
changed. A. change is produced which is not heat. When 
a piece of coal burns, then, its composition is changing, 
and as a result of this change heat is produced. The heat 
is, therefore, produced by a chemical change in the coal, 
and we may say that the motion of the steam-engine is the 



4 THE ELEMENTS OF CHEMISTRY. 







result of the chemical change taking place in the coal or 

wood which, in burning, produces the heat 

Heat Causes Chemical Change. — Just as chemical change 

produces heat, as in the burning of a piece of wood, so 

heat causes chemical changes. 

Experiment 1. — In a clean, dry test-tube put enough white 
sugar to make a layer i to i inch thick. Hold the tube in 
the flame of a spirit-lamp or a laboratory ourner 
as shown in the figure. What changes take 
place ? What do you notice on the sides of the 
tube ? What remains behind ? What is its color 
and taste? Does it dissolve in water? Is it 
sugar? Is the change which has taken place 
chemical or physical ? What caused it ? 

Experiment 2. — From a piece of glass tubing 
of about J inch internal diameter cut off a 
piece about four inches long by making a martf 
across it with a triangular file, and then seizing 
it with both hands, one on each side of the 
mark, pulling and at the same time pressing 
Fig. i. slightly as if to break it. Clean and dry it, 

and hold one end in the flame of a laboratory burner until it melts 
together. During the melting twirl the tube constantly between 
the finger and thumb so that the heat may act uniformly upon it. 
After it has cooled down put into it enough red oxide of mercury 
(mercuric oxide) to form a layer \ inch thick. Heat the tuDe as 
in the last experiment. — What change in color do you notice? 
What is deposited on the sides of the tube ? During the heating 
insert a splinter of wood with a spark on the end into the tube. 
What follows? Take it out and put it back a few times. Is 
there any difference between the burning in the tube and out of 
it ? What difference ? How do you know that the red substance 
which you put into the tube has been changed ? Is the change 
chemical or physical ? What caused the change ? 

Chemical Change Caused in Other Ways. — In the two 

experiments just performed heat caused chemical change. 
Chemical changes can be produced in other ways. The 
simplest way is by bringing substances together. 



CHEMICAL CHANGES— PHYSICAL CHANGES 



Experiment 3. — Examine a piece of calc-spar or marble. 
Notice whether it is hard or soft. Heat a small piece in a glass 
tube snch as used in Experiment 2. Does it change in any way ? 
Does it dissolve in water? In order to learn whether a substance 
is soluble in water proceed as follows : Put a piece about the size 
of a pea in a test-tube with distilled water. Thoroughly shake, and 
then, as heating usually aids solution, boil. Now pour off a few 
drops of the liquid on a piece of platinum-foil* or a watch-glass, 
and by gently heating cause the water to pass off as steam. If 
there is anything solid in solution there will be something solid 
left on the platinum-foil or watch-glass. If not, there will be 
nothing left. — Knowing now the general properties of the calc- 
spar or marble you will be able to determine whether it is 
changed or not. Treat a small 
piece with dilute hydrochloric 
acid. What takes place? After 
the action has continued for 
about half a minute insert a 
lighted match in the upper part 
of the tube. Does the match 
continue to burn ? Does the sub- 
stance in the tube burn ? Is the 
invisible substance in the upper 
part of the tube ordinary air? 
Why not? Does the solid sub- 
stance disappear ? In order to tell 
whether it has been changed 
chemically the hydrochloric acid Fig. 2. 

must be gotten rid of. This can be done by boiling it, when 
it passes off in the form of vapor, just as water does, and then 
whatever is in solution will remain behind. For this purpose put 
the solution in a small, clean porcelain evaporating-dish, and put 
this on a vessel containing boiling water, or a water-bath. The 
operation should be carried on in a place where there is a good 
draught, so that the vapors will not collect in the working-room. 
They are not poisonous, but they are annoying. The arrange- 




* The expensive metal platinum is much used in chemical labora- 
tories, for the reason that it resists the action of heat and of most 
substances. 



6 THE ELEMENTS O^BSEMISTBY. 

ment for evaporating is illustrated in Fig. 2. After the liquid 
has evaporated and the substance in the evaporating-dish is dry, 
examine it and carefully compare its properties with those of the 
substance which was put into the test-tube. Is it the same sub- 
stance ? Is it hard or soft ? Does it change when heated in a 
tube? Is there an appearance of bubbling when hydrochloric 
acid is poured on it ? Does it dissolve in water ? Does it change 
when allowed to lie in contact with the air ? 

Experiment 4. — Bring together in a test-tube a small piece 
of copper and some moderately dilute nitric acid. Hold the 
mouth of the tube away from your face and do not inhale the 
vapors. What is the appearance of the vapors given off ? What 
is the appearance of the liquid in the tube ? Does the copper dis- 
solve ? Examine the solution, as in the preceding experiment, 
and see what has been formed. What are the properties of the 
substance found after the liquid has evaporated ? Is it colored ? 
Is it hard or soft ? Does it change when heated in a tube ? Is it 
soluble in water ? Does it in any way suggest the copper with 
which you started ? 

Experiment 5. — Try the action of dilute sulphuric acid on a 
little zinc in a test-tube. An invisible gas will be given off. 
Apply a lighted match to the mouth of the tube. What takes 
place ? After the zinc has disappeared evaporate the solution as 
before. Carefully compare the properties of the substance left 
behind with those of zinc. 

Experiment 6.— Hold the end of a piece of magnesium rib- 
bon about eight inches long in a flame until it takes fire. Then 
hold the burning substance quietly over a piece of dark paper, so 
that the light, white substance which is formed may fall upon the 
paper. Compare the properties of this product with those of 
magnesium. 

Experiment 7. — In a small dry flask of about four ounces 
capacity put a bit of granulated tin or of pure tin-foil. Pour 
upon it enough concentrated nitric acid to cover it. If no change 
takes place at first, heat gently, and presently you will have 
evidence that change is taking place. Is there anything in this 
experiment whio^ suggests Experiment 4 ? What is left behind 
after the action is finished? Compare the properties of the 
product with those of tin. 



CHEMICAL CHA^Fm—PHYSICAL CHANCES. 7 

Solution Aids Chemical Action. — In the cases just studied 
it was only necessary to bring the substances together, 
when they acted at once. In each case one of the sub- 
stances used was a liquid. Solids do not, as a rule, act 
upon one another as re^ily as liquids act upon solids, for 
the reason. that the small particles of which the solids are 
made up cannot be brought as closely together as the par- 
ticles of liquids. 

Experiment 8. — Mix together in a dry mortar a little dry 
tartaric acid and about an equal quantity of dry bicarbonate of 
soda (sodium bicarbonate). Do you see any evidence of action ? 
Now dissolve a little tartaric acid in water in a test-tube, and a 
little carbonate of soda in water in another test-tube. Pour 
the tv/o solutions together. What evidence have you now that 
action takes place ? Pour water upon the dry mixture first made. 
Does action take place? What causes the bubbling? Will a 
match burn in the gas ? In which experiment already performed 
was a similar gas obtained ? 

Experiment 9. — Mix together in a dry mortar a little dry 
sulphate of iron (green vitriol) and a little dry ferrocyanide of po- 
tassium (yellow prussiate of potash). Does action take place? 
Make a solution of each of the two substances and pour them 
together. What evidence have you that action takes place? 
I^our water on the dry mixture. Does action take place ? 

Summary. — From the experiments it will be seen (1) that 
heat causes chemical change; (2) that in some cases simple 
contact of substances is sufficient to cause chemical change; 
(3) that solution aids chemical change. In all the cases 
of chemical action thus far studied one thing was observed, 
viz.,, that the substances which were acted upon lost their 
own properties and new substances were formed. This 
^true in all cases of chemical action, and the truth maybe 
stated thus: 

Whenever two or more substances act upon one another 



8 THE ELEMENTS OF CHEMISTRY. 

chemically they lose their own properties, and new sub- 
stances are formed with entirely different properties. 

Difference between Combining Chemically and simply 
Mixing. — By mixing is meant bringing things together 
closely, so that the particles of on^ehall be in contact with 
the particles of the other. We mix salt and sugar by put- 
ting them together in a vessel and shaking them, or by 
stirring as with a pestle in a mortar. The longer we stir 
the more closely the substances are brought together. But 
no matter how long we may stir the mixture, it remains a 
mixture and contains both sugar and salt. In some cases, 
by stirring, chemical action can be brought about, but 
generally not. 






Experiment 10. — Mix two or three grams of powdered roll- 
sulphur and an equal weight of % very fine iron filings in a small 
dry mortar. Examine a little of the mixture with a microscope. 
Can you distinguish the particles of sulphur and those of iron ? 
Pass a small magnet over the mixture. Are particles of iron 
drawn out of the mixture ? Has chemical action taken place ? 

Experiment 11. — Pour two or three cubic centimetres of 
bisulphide of carbon on a little powdered roll-sulptor in a dry test- 
tube. Does the sulphur dissolve ? Treat iron filings in the same 
way. Does the iron dissolve ? Now treat a small quantity of the 
mixture prepared in Experiment 10 with bisulphide of carbon. 
After the sulphur is dissolved pour off the solution in a good- 
sized watch-glass and let it stand. Examine what is left in the 
test-tube. Is it iron ? After the liquid has evaporated examine 
what is left on the watch-glass. Is it sulphur ? 

Experiment 12. — Mix three grams of finely powdered roll- 
sulphur and three grams of fine wrought-iron filings or pow- 
dered iron to be had of the druggists. Put the mixture in a 
dry test-tube. Heat gently at first and notice the changes. At 
first the sulphur melts and becomes dark-colored. It may even 
take fire. But soon something else takes place. The whole mass 
begins to glow, and if you at once take the tube out of the flame 
the mass will continue to glow, becoming brighter. This will 



CHEMICAL CHANGES— PHYSICAL CHANGES. 9 

soon stop; the mass will grow dark and gradually cool down. 
As soon as it reaches the ordinary temperature, break the tube 
and put the contents in a mortar. Does the mass look like the 
mixture of sulphur and iron with which you started ? An exam- 
ination with the microscope, the magnet, and bisulphide of car 
bon will prove that, while there may be a little iron left and pos- 
sibly a little, sulphur, most of the bluish-black mass is neither 
iron nor sulphur, but a new substance with properties quite dif- 
ferent from those of iron and of sulphur. 

What has Become of the Iron and the Sulphur ? — In the 

last experiment a new substance was formed by the action 
of sulphur upon iron. Neither substance has been de- 
stroyed, but both hayo combined in a much more intimate 
way than when they were simply mixed together. This 
kind of combination which causes the properties of the 
combining substances to disappear is called chemical com- 
bination. Nothing is lost in the act, as has been shown by 
weighing the substances before and after action. 

Mechanical Mixtures and Chemical Compounds. — In a 
mixture the substances are unchanged. They exist side by 
side. In a chemical compound the substances ivhich are in 
combination are completely changed. They are so intimate- 
ly combined that they cannot be recognized by any ordinary 
means. 

Compounds and Elements. — Most of the substances found 
in nature are made up of several others. Wood, for exam- 
ple, is very complex, containing a large number of distinct 
substances intimately mixed together. Some of these can 
be got out separately, but it is impossible to get them 
all out separately with the means at present at our com- 
mand. Most of the rocks met with, and the different kinds 
cf earth, as clay, sand, etc., are also quite complex, and it 
is in most cases difficult to get out the substances contained 



10 THE ELEMENTS OF CHEMISTRY. 

in them. By proper methods, however, it is possible to 
decompose the complex substances found in nature so as to 
get simpler ones, and these again can usually be decom- 
posed into still simpler ones which cannot be decomposed 
by any means known to us. Substances which we cannot 
decompose into simpler ones are called elements. Now, al- 
though there are thousands and thousands of different 
kinds of substances met with in nature, these are really 
made up of a comparatively small number of simple sub- 
stances or elements. The number of elements thus far 
discovered is between sixty and seventy, but the larger 
number of these are rare, and we might have a very ex- 
cellent knowledge of the essentials of chemistry without 
any knowledge of these rare elements. We shall find that 
most things we have to deal with are really made up of 
about a dozen elements, and that most of the chemical 
changes which are taking place around us, and which we 
need to study in order to get an insight into the nature of 
chemical action^ take place between this small number of 
elements. 

An element is a substance which we cannot decompose into 
simpler substances. 

A compound is a substance ivhich can be decomposed into 
simpler ones. A compound contains two or more elements 
held together chemically. 

Examples of Elements and Compounds. — As examples of 
elements may be mentioned iron, copper, tin, silver, gold, 
(sulphur, and lead. As stated in the last paragraph, they 
are called elements for the reason that they cannot be de- 
composed into simpler substances. Among familiar com- 
pounds may be mentioned water, common salt or sodium 
chloride, blue vitriol or copper sulphate^ chlorate of potash 



CHEMICAL CHANGES-PHYSICAL CHANGES, 11 

or potassium chlorate, marble or calcium carbonate, sand 
or silicon dioxide. Each of these compounds consists of 
two or more elements held together in chemical combina- 
tion. Water can be decomposed by various methods into 
two substances known as hydrogen and oxygen, and the 
sum of the weights of the hydrogen and oxygen obtained 
from a given weight of water is exactly equal to the weight 
of the water decomposed. Sodium chloride can be decom- 
posed into the two elements sodium and chlorine, and the 
weight of the sodium added to the weight of the chlorine 
exactly equals the weight of the sodium chloride. On the 
other hand, the composition of an element cannot be 
changed without adding something to it. 

Chemical Action. — Just as the earth attracts all bodies 
to it in some mysterious way which we call gravitation, 
just as the magnet attracts pieces of iron, so substances are 
drawn together chemically and, if they come in contact 
under the proper conditions, chemical action takes place. 
By this is meant that some change in composition is brought 
about ; that the substances which are brought together dis- 
appear and new ones make their appearance. But the 
quantity of matter remains the same. The elements ar- 
range themselves differently. 

Three Kinds of Chemical Action. — The numerous cases 
of chemical action may be divided into three classes: (1) 
combination; (2) decomposition ; and (3) double decompo- 
sition or metathesis. As an example of combination the 
case of the action of iron on sulphur may be taken. The 
two elements combine directly, forming a compound known 
as iron sulphide. The action may be represented thus: 
Iron + Sulphur — Iron Sulphide. 

A good example of decomposition is that of the action of 



12 THE ELEMENTS OF CHEMISTRY. 






heat on the red oxide of mercury or mercuric oxide (see 
Experiment 2). When this substance is heated two things 
are obtained from it: an invisible gas, oxygen, which passes 
out of the vessel and which can be detected by the fact that 
substances burn in it more readily than they do in air ; 
and a silvery-looking liquid, which is quicksilver or mer- 
cury. The action in this case may be represented thus: 

Mercuric Oxide = Mercury + Oxygen. 

In double decomposition two or more substances act upon 
one another and give rise to the formation of two or more 
new ones. Thus when hydrochloric acid acts upon marble 
(see Experiment 3) two substances, calcium chloride and 
carbonic acid, are formed. This may be represented thus: 

Hydrochloric Acid + Calcium Carbonate (or marble) = 
Calcium Chloride + Carbonic Acid. 

Most cases of chemical action which we have to deal with 
are of the third kind. 

The Cause of Chemical Action. — It is evident from what 
we have already learned that there is some power which 
can hold substances together in a very intimate way, so in- 
timate that we cannot recognize them by ordinary means. 
We do not know what causes sulphur and iron to combine, 
but we know that they do combine. Similarly, we do not 
know what causes a stone thrown in the air to fall back 
again, but we know that it falls back. It is true we say 
that the cause of the falling of the stone is the attraction of 
gravitation, but this does not give us any information, for, 
if we ask what the attraction of gravitation is, we can only 
answer that it is that which causes all bodies to attract one 
another. So, too, we may say that the cause of the chemi- 
cal union of substances is chemical attraction. But in so 



CHEMICAL CHANGES-PHYSICAL CHANGES. 13 

doing we are only giving a name to something about which 
we know nothing except the effects which it produces. 

Importance of Chemical Action. — If this power, what- 
ever it may be, should cease to operate, what would be the 
result? As far as we can see all substances known to be 
chemical compounds would be decomposed into the elements 
of which they are composed, and there would be only about 
sixty or seventy different kinds of substances. All living 
things would cease to exist, and in their place we should 
have three invisible gases and something very much like 
charcoal. Mountains would crumble* to pieces, and all 
water would disappear giving two invisible gases. The 
processes of life in its many forms would be impossible. 
These considerations will suffice to show the great impor- 
tance of the subject of chemistry, and how impossible it 
is without some knowledge of this subject to form any 
conception in regard to the most important phenomena of 
the universe. 

Occurrence of the Elements. — As has already been stated 
(p. 10), not more than a dozen elements enter largely into 
^he composition of the earth. It has been estimated that 
the solid crust of the earth is made up approximately as 
represented in this table: 

Oxygen 44-48 per cent. 

Silicon 22-36 " 

Aluminium. 6-10 " 

Iron ^ 2-10 ' * 

Calcium 1-7 " 

Magnesium 0.1- 3 " 

Sodium 2- 3 " 

Potassium 1.5-3 " 

While oxygen forms a large proportion of the solid crust 
of the earth, it forms a still larger proportion (eight ninths) 



14 THE ELEMENTS OF CHEMISTRY. 

of water, and about one fifth of the air. Carbon is the 
principal element entering into the structure of living 
things, while hydrogen, oxygen, and nitrogen also are 
essential constituents of animals and plants. Nitrogen 
forms about four fifths of the air. 

The Names of the Elements.— The names of the elements 
are formed in many different ways. The name chlorine is 
derived from a Greek word meaning greenish yellow, as this 
is the color of chlorine. Bromine comes from a Greek word 
meaning a stench, a prominent characteristic of bromine 
being its bad odor. Hydrogen is formed from two Greek 
words, one of which means water and the other to produce, 
signifying that it enters into the composition of water. 
Potassium is an element found in potash, and sodium is 
found in soda„ 

The Symbols of the Elements. — It is convenient to use 
abbreviations for the names of the elements and com- 
pounds. Thus, instead of oxygen we may write simply 0, 
for hydrogen E, for nitrogen N, etc. Very frequently the 
first letter of the nam? of the element is used as the symbol. 
If the names of two or more elements begin with the same 
letter, this letter is used, but some other letter of the name 
is added. Thus, B is the symbol of boron, Ba of barium, 
Bi of bismuth, etc. In some cases the symbols are de- 
rived from the Latin names of the elements. Thus, the 
symbol of iron is Fe, from fer rum, ; of copper, Cu, from 
cuprum ; of mercury, Hg, from hydrargyrum, etc. The 
symbols of the more common elements will soon become 
familiar by use. It is not desirable to attempt to commit 
them to memory at this stage. 

List of the Elements and their Symbols. — In the table 
here given the names of those elements which are most 



CHEMICAL CHANGES-PHYSICAL CHANGES. 15 



widely distributed, and which form by far the largest part 
of the earth, are printed in small capitals. The names 
of those which are very rare are printed in italics. 



Aluminium Al 

Antimony Sb 

Arsenic As 

Barium Ba 

Bismuth Bi 

Boron B ! 

Bromine Br 

Cadmium Cd I 

Ccesium Cs j 

Calcium Ca I 

Carbon C 

Cerium Ce I 

Chlorine CI | 

Chromium Cr 

Cobalt Co 

Columhium Cb 

Copper Cu 

Didumium Di 

Erbium E 

Fluorine F 

Gallium Ga j 

Glucinum Gl i 

Gold Aul 



Hydrogen H 

Indium In 

Iodine I 

Iridium Ir 

Iron Fe 

Jjanthanum ... . . .La 

Lead Pb 

Lithium Li 

Magnesium Mg 

Manganese Mn 

Mercury Hg 

Molybdenum Mo 

Nickel Ni 

Niobium . Nb 

Nitrogen N 

Osmium . . . Os 

Oxygen O 

Palladium........ Pd 

Phosphorus P 

Platinum Pt 

Potassium K 

Rhodium Rh 

Rubidium Kb 



Ruthenium Ru 

Samarium Sm 

Scandium Sc 

Selenium Se 

Silicon Si 

Silver Ag 

Sodium .Na 

Strontium Sr 

Sulphur S 

Tantalum Ta 

Tellurium Te 

Thallium Tl 

Thorium Th 

Tin Sn 

Titanium Ti 

Tungsten W 

Uranium U 

Vanadium Y 

Ytterbium Yt 

Yttrium Y 

Zinc Zn 

Zirconium Zr 



What We Shall Study. — -In the course which you have 
begun you will study only the most common elements and 
their action upon one another. In this way you will be 
able to learn much about the chemistry of many interesting 
things, such as burning, the rusting of iron, the growth of 
plants and animals, the extraction of useful metals from 
their ores, the manufacture of illuminating-gas, of soap, 
etc., etc., and at the same time you will acquire a know! 
edge of the general principles of chemistry which will 
enable you to take a more intelligent view of the universe 
than you can without this knowledge. 



16 TEE ELEMENTS OF CHEMISTRY 



CHAPTEE II. 
THE CHEMISTRY OF THE AIR. 






The Air Causes Chemical Changes. — One of the most 
interesting, most common, and most important chemical 
changes with which we are familiar is that which is known 
as burning. No matter how we may begin the study of 
chemical facts, we are at once brought face to face with the 
fact that the air takes part in chemical change. 

Experiment 13. — In a small porcelain crucible arranged .as 

shown in Fig. 3 put a small piece of lead. Heat by means of a 

laboratory burner, and notice the changes which take place. 

After the lead is melted stir with a thick iron 

wire while heating. Continue to heat and stir 

until the substance is no longer liquid. What 

is its appearance now? Let it cool. Is it 

lead ? What difference is there between the 

action in this case and in the case of melting 

ice and cooling the water down again ? Which 

is chemical action and which physical action ? 

Fig. 3. Why ? 

Experiment 14. — Heat a piece of zinc in the same way as you 

have just heated lead. What changes take place ? 

Experiment 15. — Heat a piece of tin in the same way. What 
changes take place ? 

What Caused the Changes ? — By heating lead, zinc, and 
tin in the air, then, they are changed to powders which do 
not melt. The question will suggest itself, does the heat 
alone cause these changes or has the air something to do 
with them ? The air alone plainly does not cause the 
changes, for they do not take place until the substances are 




THE CHEMISTRY OF THE AIR. 17 

heated. To learn whether the air has anything to do with 
them we shall have to heat the substances in such a way as 
to keep the air from getting at them. This can be done 
by putting in the vessel something which melts and which 
will float on the melted metal. Such a substance is ordi- 
nary borax. 

Experiment 16. — Kepeat Experiments 13, 14, and 15, adding in 
each case enough borax to form a complete cover to the metal 
after both are melted. Do the metals melt ? Are they changed 
to powders as in the previous experiments ? 

Many Similar Facts are Known. — The examples given 
above are only a few of a large number of similar ones 
mown. Hence the statement that many metals when 
heated in the air undergo chemical change and are con- 
verted into powders which do not melt. The powders are 
formed by the action of the air on the heated metals, for 
if the air be kept away from the metals the changes do not 
take place. 

The Metals Increase in Weight when Heated in the Air. 
—If you were to weigh the metals used in Experiments 13, 
14, and 15 and then weigh the powders obtained, you would 
find that in each case the powder weighs more than the 
metal. This fact taken together with the others already 
learned shows that there is something in the air which at 
high temperatures combines with the metals tin, zinc, and 
lead. 

Burning in the Air. — The phenomenon of burning takes 
place in the air, and the question suggests itself, has the 
air anything to do with the burning ? You know that if 
you shut up a stove completely the fire dies down, and 
unless the draught-door is opened the fire goes out. If you 
want the fire to burn more actively you open the draught- 
2 



18 THE ELEMENTS OF CHEMISTRY. 

doors when air is drawn in and the burning is made to 
take place more rapidly. A fire burns better when air is 
blown into it with a bellows. A candle is put out when 
anything is brought down upon the flame in such a way as 
to keep out the air. When a smouldering fire is covered 
with ashes it goes out. All these facts, which are well 
known to every one, make it appear probable that the aii 
has something to do with burning, but they do not show 
what. In order to learn this we shall have to experiment 
carefully, noticing everything that takes place. 

Experiment 17. — Fix a short bit of candle on a large flat cork 

or a block of wood. Light the candle and place it with the block 

on the surface of water contained in a pail or some other appro* 

priate vessel. Place over it a good- sized glass vessel, either a 

wide-mouthed bottle or a good-sized fruit- jar, as represented in 

Fig. 4, so that the candle and cork are in the glass vessel and the 

r\ mouth of the vessel is beneath the 

^^"^^1^ surface of the water. Hold it in this 

mi i'llh'^l ■ IB position for a few minutes and ob- 

■1 'l^c^illNB serve what takes place. Does the 

^ Hl"' i"r jjfflK-'-^^g JiBli I ;,{fe'^ can dle continue to burn ? Is all the 

^fflT||fl ijjjI^SFj^flHl^^ a ^ r contained in the vessel used up 

* - : -| |1 p|3& when the candle goes out ? Try the 

Slllfii experiment a second time, and when 

\^ "'li ^ ^ m^^^ ^^^^" the candle is nearly out raise the 

Fig. 4. glass vessel so that air can get in. 

Does this make any difference ? What difference ? What do 

these experiments prove ? 

A Candle Will Not Burn in the Air that is Left.— If, 

after the candle has gone out, you place your hand or a 
ground-glass plate over the mouth of the vessel and turn 
it mouth upward, and then insert into it a lighted candle 
on a wire, the candle will be extinguished. You see that 
the air which is left in the vessel after a candle has binned 
in it and gone out is not the same as ordinary air. 



THE CHEMISTRY OF THE AIB. 



19 



Experiment 18. — Try the experiment just mentioned. The 
candle on the wire should be arranged as shown in Fig. 5. 

Does the Candle Increase in Weight ? — 
You know that in burning the candle 
gradually disappears, and from this you 
would be inclined to think that it is de- 
stroyed. But if you were to collect the 
smoke which is given off and weigh it, you 
would find that it weighs more than that 
part of the candle which has burned up. 
So that instead of there being a loss of 
matter there is apparently a gain. 




Fig. 5. 



Experiment 19. — On one pan of an appropriate balance place 
a candle, and directly over it suspend a wide glass tube contain- 
ing pieces of caustic soda, a substance which has the power to 
absorb most of the smoke given off from the burning candle. 
Place a similar glass tube with caustic soda on the other pan of 
the balance and exactly balance the two pans. Now light the 
candle, and in the course of a few minutes the pan with the 
candle on it will sink, showing that it is heavier than the other. 

One Fifth of the Air is Used 
up when Anything Burns in 
a Closed Vessel.— By careful 
experiments which it would 
be difficult to repeat here it 
has been shown that only one 
fifth of the air is capable of 
keeping up the process of 
burning, while the rest is an 
inactive substance in which 
burning cannot take place. 
If , for example, you could heat a piece of lead or zinc in 
a closed vessel for a time, then let it cool and open the 




Fig. 6. 



20 THE ELEMENTS OF CHEMISTRY. 

vessel under water, you would find that water would rush in 
and fill about one fifth of the vessel, showing that this 
much air had been used up. If you should weigh the metal 
before and after heating you would find that it had in- 
creased in weight, and if you should weigh the air used up 
you would find that its weight is exactly equal to the in^ 
crease of weight of the metal. A great many experiments 
of this kind have been performed, and they have shown 
that when a substance burns it uses up something from the 
air and increases in iveight exactly as much as the air loses. 
The Air Consists Mainly of Two Substances. — The air 
then consists of two substances, only one of which can keep 
up the process of burning. This one is known as oxygen. 
The other, in which things cannot burn, is known as nitro- 
gen. Besides these the air always contains smaller quanti- 
ties of other substances, particularly water vapor, carbonic 
acid (or carbon dioxide), and ammonia. We shall soon 
study these substances and see of what value they are in 
the air. Oxygen and nitrogen are called elements because 
no one has been able to decompose them and get anything 
simpler from them. 






OXYGEN. 21 



CHAPTER III. 
OXYGEN. 

Occurrence of Oxygen. — Oxygen is the most widely dis- 
tributed element, and it occurs also in very large quantity. 
It has been stated that it forms between forty and fifty 
per cent of the solid crust of the earth, eight ninths of 
water and one fifth of the air by bulk. 

Preparation of Oxygen. — We have oxygen around us in 
great abundance, but it is mixed with nitrogen, and it is 
difficult to separate the two so as to get the oxygen. The 
easiest way to get oxygen is by heating something which 
contains it. One of the simplest examples of this kind is 
the oxide of mercury, which when heated gives mercury and 
oxygen. When mercury itself is heated in the air for some 
time to very near its boiling point it is gradually changed 
to a red powder, just as lead and tin and zinc are changed 
to powders when heated in the air. This powder is a com- 
pound of mercury and oxygen. When the compound is 
heated to a high temperature it is decomposed into its 
elements, mercury and oxygen. 

Collection of Oxygen. — The oxygen given off from the 
oxide of mercury is most conveniently collected by causing 
it to displace water. For this purpose the apparatus 
should be arranged as represented in Fig. 7. On now 
heating the oxide, the oxygen which is set free necessarily 



22 



THE ELEMENTS OF CHEMISTBY. 



passes through the narrow tube and escapes beneath the 
mouth of the inverted glass vessel which is filled with 
water. The gas being lighter than water rises and the 
water is displaced. The oxide of mercury should be heated 
in a tube made of hard glass closed at one end. 

Oxygen Made from Potassium Chlorate. — Another sub 
stance which readily gives up oxygen when heated is po- 
tassium chlorate or, as it is commonly called, chlorate of 
potash. This is manufactured in large quantities and is 
easily obtained. It contains the three elements potas- 




Fig. 7. 



slum, chlorine, and oxygen. When heated it gives up the 
oxygen, and a compound of potassium and chlorine, knowi 
as potassium chloride, very much like common salt, it 
left behind. 

Experiment 20. — Arrange an apparatus as shown in Fig. 8. 
A represents a flask of 100 c.cm. capacity. By means of a good- 
fitting rubber stopper one end of the bent glass tube B is con- 
nected with it, and the other end, which should turn upward 
slightly, is placed under the surface of the water in C. In A put 
4 to 5 grams (about an eighth of an ounce) potassium chlorate, 
and gently heat by means of a lamp. When gas comes off freely 






OXYGEN. 



23 



bring the inverted cylinder B filled with water over the end of 
the tube, and let the bubbles of gas rise in the cylinder. Exam- 
ine the gas by placing a glass plate over the mouth of the vessel 
containing it and inverting it. Insert into it a stick with a spark 
on its end. What takes place ? Is the gas contained in the ves- 
sel ordinary air ? 




Fig. 8. 



Oxygen Made by Heating a Mixture of Potassium Chlo^ 
rate and Manganese Dioxide. — The most convenient way to 
make oxygen in the laboratory is to heat a mixture of 
equal parts of potassium chlorate and manganese dioxide 
or " black oxide of manganese." This mixture gives off 
oxygen very readily when heated. The potassium chlorate 
alone is decomposed under these circumstances,, the man- 
ganese dioxide remaining unchanged. It is not known 
how the manganese dioxide helps the action. 

Experiment 21. — Mix 25 to 30 grams (or about an ounce) of 
potassium chlorate with an equal weight of coarsely powdered 



24 



THE ELEMENTS OF CHEMISTRY* 




manganese dioxide in a mortar Heat the mixture* in a glass 
retort arranged as shown in Fig. 9, and collect the gas by 

displacement of water in ap 
propriate vessels — cylinders, bell 
glasses, bottles with wide mouths, 
etc. 

Physical Properties of Oxy- 
gen. — Having thus learned how 
to get oxygen, you may proceed 
to study its properties. In the 
first place, the gas is invisible. 
The slight cloud which ap- 
pears in the vessels when the 
gas is first collected is due 
to the presence of a very 
small quantity of a substance 
which is not oxygen. If the vessels are allowed to stand 
for a few minutes the cloud will disappear, and the vessels 
will look the same as if they were filled with air The 
gas is tasteless and inodorous. [Inhale a little from one of 
the small bottles.] It is slightly heavier than the air. 
When subjected to an extremely high pressure and low 
temperature it becomes liquid. The properties of oxygen 
to which reference has thus far been made are its physical 
properties. These are its appearance, taste, smell, relative 
weight, and changes in its condition, which still leave it 
in the elementary form or uncombined chemically. 



FiGo 9. 



* Black oxide of manganese is sometimes adulterated with other 
substances, and wiaen heated with potassium chlorate it may then 
give rise to explosions. It should he tested before using by mixing 
a little with potassium chlorate and heating in a test tube. If the de- 
composition takes place quietly the substance may be used for the 
preparation of oxygen. 



OXYGEK 25 

Chemical Conduct of Oxygen. — In order to get an idea 
of the way in which oxygen acts upon some simple sub- 
stances under ordinary circumstances a few experiments 
should be performed. We want to learn: What changes 
oxygen can effect in other substances; what conditions 
are necessary in order that it may act chemically; what 
products are formed, etc., etc. 

The Action of Oxygen at the Ordinary Temperature. 

Experiment 22. — Turn three of the bottles containing oxygen 
with the mouth upward, leaving them covered with glass plates. 
Into one introduce a little sulphur in a so-called deflagrating- 
spoon, which is a small cup of iron or brass attached to a stout 
wire which passes through a round metal plate, usually of tin 
(see Fig. 10). In another put a little charcoal (carbon), and in a 
third a piece of phosphorus * about the size of a pea. Let them 
stand quietly and notice what changes, if any, take place. 

What these Experiments Show. — These experiments show 
that oxygen does not act upon sulphur and carbon when 
brought in contact with them, and that the action upon 
phosphorus is slight. We might perform experiments of 
this kind with a great many substances,, and we should 
reach the conclusion that at the ordinary temperature oxy- 
gen does not readily act upon substances. Indeed, as the 
air contains a considerable proportion of oxygen, it is clear 
that oxygen does not readily act upon substances at ordi- 
nary temperatures or action would constantly be taking place 



* Phosphorus should be handled with great care. It is always 
kept under water, usually in the form of sticks. If a small piece is 
wanted, take out a stick ™ith a pair of forceps, and put it under water 
in an evapora ting-dish. While it is under the water cut off a piece of 
the size wanted. Take this out by means of a pair of forceps, lay it 
for a moment on a piece of filter-paper, which will absorb most of the 
water; then quickly put it in a spoon. 



26 THE ELEMENTS OF CHEMISTRY. 

between the air and many of the substances exposed 
to it 
Slow Action of Oxygen at the Ordinary Temperature.— 

Upon some substances oxygen does act even at ordinary tem- 
perature. Some metals, as iron, become covered with a 
layer of rust when exposed to the air. This is due partly, 
at least, to the action of the oxygen of the air. Wood and 
other vegetable substances undergo slow decomposition 
when exposed to the air, in consequence of the action of 
the oxygen. Animal substances undergo decomposition 
comparatively readily when exposed to the air. The pro- 
cess of decay is partly due to the action of oxygen at the 
ordinary temperature. 

The Action of Oxygen in Animal Bodies. — The most im- 
portant illustration of the action of oxygen at low tempera- 
tures is that which takes place in our bodies and the bodies 
of all animals. The food which we partake of undergoes 
many changes; some of the substances uniting with oxygen. 
Then , too, we take large quantities of oxygen into our lungs 
inbreathing. This acts upon various substances which are 
presented to it in the lungs; it combines with them, form- 
ing other substances which can easily be got rid of. More 
will be said in regard to the breathing of animals and plants 
when the subject of carbon and its compounds with oxygen 
is taken up. 

The Action of Oxygen upon Heated Substances. — Sup- 
pose that before putting them in the oxygen we heat the 
substances used in Experiment 22, what will then take place? 

Experiment 23. — In a deflagrating-spoon set fire to a little sul- 
phur and let it burn in the air. Notice whether it burns with 
ease or with difficulty. Notice the odor of the fumes which are 




OXYGEN. 27 

given off. Now set fire to another small portion and introduce it 

in a spoon into one of the vessels containing oxygen, as shown in 

Fig. 10. Does the sulphur burn more 

readily in the oxygen or in the air? 

Notice the odor of the fumes given off. 

Is it the same as that noticed when the 

burning takes place in the air ? 

Experiment 24. — Perform similar 
experiments with charcoal. 

Experiment 25. — Burn a small piece 
of phosphorus in the air and in oxygen. 
In the latter case the light emitted from 
the burning phosphorus is so intense Fig. 10. 

that it is painful to some eyes to look at it. After the burning is 
over let the vessel stand. Does it become clear ? 

What Took Place in these Experiments? — In the first 
place, the substances were simply heated before they were 
introduced into the oxygen. Nothing was added to them. 
It is clear, therefore, that while oxygen does not act upon 
these substances at the ordinary temperature, it does act 
upon them at higher temperatures. But what does the ac- 
tion consist in? We can determine this only by a careful 
study of the substances before and after the action. We 
must know not only what substances are brought together, 
hit also icliat the weight of each is; and we must know what 
substances are left behind, and the exact iveight of these. 
By means of accurate experiments it has been shown re- 
peatedly that the substances which burn in oxygen disap- 
pear as such, and that in each case a definite quantity of 
oxygen is also used up. The result of the experiments can 
be stated thus: The iveight of the substance hirned plus 
the iveight of the oxygen used up is exactly equal to the 
weight of the product formed. 



28 THE ELEMENTS OF CHEMISTRY. 

Burning is Combining with Oxygen. — From what we 
have learned we may conclude that when a substance hums 
in oxygen the act consists in the chemical combination of 
the two. 

Burning in the Air. — To determine whether burning in 
the air is the same act as burning in oxygen it is neces- 
sary to burn the same things in air and in pure oxygen 
and see whether the products are the same. This has 
been done a great many times, and always with the same 
result. Whether a substance burns in the air or in pure 
oxygen the same product is formed., and nothing else. 
It is therefore certain that the act of burning in the air is 
due to the presence of oxygen. As we have already seen^ 
there is another substance present in the air in large quan- 
tity, and it is due to this fact that burning does not take 
place as readily in the air as in oxygen. 

Combustion. — By the term combustion in its broadest 
sense is meant any chemical act which is accompanied 
by an evolution of light and heat. Ordinarily, however, 
it means the union of substances with oxygen as this 
union takes place in the air, with evolution of light and 
heat. Substances which have the power to unite with oxy- 
gen are said to be combustible, and substances which have 
not this power are said to be incombustible. Most of the 
elements combine with oxygen under proper conditions, 
and are therefore combustible. Most compounds formed 
by the union of oxygen with combustible substances are 
incombustible. They contain oxygen and they cannot di- 
rectly combine with any more. 

Some Substances which do not Burn in the Air Burn 
in Oxygen. — The best illustration of this fact is that of 
iron. This metal, as you know, does not burn in the air. If 






OXYGEN. 29 

it did, all our stoves,, iron vessels, and iron buildings would 
burn up. In pure oxygen, however, iron burns readily. 

Experiment 26. — Straighten a steel watch-spring * and fasten 
it in a piece of metal, such as is used for fixing a defiagrating- 
spoon in an upright position; wind a little thread around the 
lower end, and dip it in melted sulphur. Set fire to this and 
insert it into a vessel containing oxygen. For a moment the sul- 
phur will burn as in Experiment 23; but soon the steel will begin 
to burn brilliantly, and the burning will continue as long as there 
is oxygen left in the vessel. The phenomenon is of great beauty, 
especially if observed in a dark room. The walls of the vessel be- 
come covered with a dark reddish-brown substance, some of 
which will also be found at the bottom in large pieces. 

Kindling Temperature. — You have seen that substances 
do not usually combine with oxygen at ordinary tempera- 
tures, but that in order to effect the union the temperature 
must be raised. If this were not the case it is plain that 
every combustible substance in nature would burn up, for 
the air supplies a sufficient quantity of oxygen for this 
purpose. Some substances need to be heated to a high 
temperature before they will combine with oxygen ; others 
require to be heated only slightly. Every combustible sub- 
stance has its kindling temperature ; that is, the tempera- 
ture at which it will unite with oxygen. Below this tem- 
perature it will not unite with oxygen. Watch a stick of 
wood burning, and watch how, as we say, ^the fire creeps" 
along it. The reason of the slow advance is simply this : 
only those parts of the stick which are nearest the burning 
part become heated to the kindling temperature. They 

* Old watch-springs can generally be had of any watch maker or 
mender for the asking. They can be straightened by pulling them 
between the thumb and some hard substance, such as a glass rod or 
a round pencil. 



30 THE ELEMENTS OF CHEMISTRY. 

take fire and heat the parts nearest them, and so on grad- 
ually throughout the length of the stick. 

Heat a Result of Combustion. — We know that whenever 
a thing burns it gives out heat, and generally light. The 
heat is a result of the act of chemical combination, and the 
light is due to the heat. Whenever chemical combination 
takes place heat is given off. It is caused by the rapid 
coming together of the particles of the substances which 
combine, just as a bullet is heated by being rapidly pro- 
jected against a hard target which stops it„ 

Chemical Energy and Chemical Work. — Any substance 
which has the power to combine with others can do chem- 
ical loorlc; it possesses chemical energy. Thus all combus- 
tible substances can do work. In combining with oxygen 
heat is given off, and this can be changed into motion. To 
go back to the example of the steam-engine, which was re- 
ferred to in Chapter I., the cause of the motion is the burn- 
ing of the fuel. 

Products of Combustion. — The substances formed in com- 
bustion are in general known as oxides. The compound 
of zinc and oxygen is called zinc oxide; that of silver and 
oxygen, silver oxide, etc. 



COMBINING WEIGHTS. 31 



CHAPTER IV. 
COMBUSTING WEIGHTS. 

Elements Combine in Definite Weights. — A certain weight 
of tin always combines with a definite weight of oxygen. 
If equal weights of sulphur and iron be mixed and caused to 
act chemically by the aid of heat, it will be found that some 
of the sulphur is left over in the uncombined state after the 
action is over. If we should take twice as much iron as 
sulphur, then, after the action, some iron would be left 
over. An extensive examination has shown conclusively 
that each chemical compound always contains the same ele- 
ments in exactly the same proportions. The compound of 
sulphur and iron always contains exactly 36.36 per cent of 
sulphur and 63.64 per cent of iron. The compound of tin 
and cxygen always contains exactly 78. 67 per cent of tin 
and 21.33 per cent of oxygen, and so on throughout the list 
% of chemical elements. 

The Law of Definite Proportions. — These facts were dis- 
covered by the united efforts of a large number of chemists 
continued through several years.' They are of great impor- 
tance. They are summed up in the general statement: 

Chemical combination always takes place between definite 
masses of substances. 

This is known as the law of definite proportions* 

What a Natural Law is. — It is simply a statement of what 
we have every reason to believe to be the truth. Every 



32 



THE ELEMENTS OF CHlJMXSTBZ 



fact known to us in regard to chemical combination is in 
accordance with the law of definite proportions. It ex- 
presses what has been learned by a study of chemical facts. 
This law,, as well as other natural laws, can never be proved 
to be absolutely true, for the reason that we cannot examine 
every case to which the law applies. But if, after examin- 
ing a very large number of cases, we find that the law holds 
true in them, we may conclude that it is true of all cases. 
When we say that all bodies attract one another, do w& 
know this to be absolutely true? Certainly not. But we 
do know that so far as those bodies are concerned which 
come under our observation the statement is true, and 
therefore we have reason to believe that it is true of all 
bodies. 

Proportions by Weight in which the Elements Combine. — 
A careful study of the figures representing the composi- 
tion of chemical compounds reveals a remarkable fact re- 
garding the relative quantities of one and the same element 
which enter into combination with other elements. The 
proportions by weight in which some of the elements com- 
bine chemically are stated in the following table : 



Sulphur 1 ; 
Oxygen 1. 


Iron 7 ; 
Oxygen 2. 


Iron 7 ; 
Sulphur 4. 


Magnesium 3 ; 
Oxygen 2. 


Tin 59 ; 
Oxygen 16. 


Zinc 65 ; 
Oxygen 16. 


Tin 59 : 
Sulphur 16. 


Zinc 65 ; 
Sulphur 32, 


Sodium 23 ; 
Oxygen 8. 


Sodium 23 ; 
Sulphur 16. 


Potassium 39 ; 
Oxygen 8. 


Potassium 39 ; 
Sulphur 16. 



You see that for iron, tin, zinc, sodium, and potassium the 
same figures are used, whether you have the compounds of 
these elements with oxygen or with sulphur, Now, if we 



COMBINING WEIGHTS. S3 

were to determine the composition of all compounds which 
contain zinc, we should find that the relative quantity of 
zinc present could, in nearly all cases, be expressed by the 
figure. 65. Similarly the quantity of sodium in sodium 
compounds could be expressed by the figure 23, and that of 
potassium in potassium compounds by 39. 

Combining Weights of the Elements. — For every element 
a certain number can be selected, such that the proportions 
by weight in which this element enters into combination 
with others can be expressed by the number or by a simple 
multiple of it. These numbers are called the combining 
iveiglits. It is not by any means an easy matter to deter- 
mine w^hich numbers are most convenient for all cases; and 
if the selection is to be determined solely by convenience, 
there may be differences of opinion as to what is most con- 
venient. We shall see a little later that while the numbers 
primarily express the combining weights and nothing else, 
and are based solely upon determinations of the composition 
of chemical compounds, they have come to have a deeper 
meaning, and are now determined by methods which you 
cannot well understand until you have gone further into 
chemistry. The facts which it is of the highest impor- 
tance that you should understand now are : 

(1) That chemical action takes place between definite 
weights of substances ; and 

(2) That the relative weights of the elements which enter 
into combination with one another can be expressed by 
numbers called the combining weights. 

Symbols of Chemical Compounds. — You have learned that 
the chemist uses a kind of short-hand to express the names 
of the elements. Instead of the name oxygen he writes 
the symbol 0, etc. Now these symbols stand not only fox 



34 THE ELEMENTS OF CHEMlSTBY. 

the names but also for the combining weights of the ele- 
ments. Thus, stands not only for the name oxygen but 
for 16 parts by weight; Fe stands for 56 parts by weight 
of iron, etc. To express a compound in the short-hand, 
the symbols of the elements contained in it are simply 
placed side by side. Thus, common salt or sodium chloride 
consists of the elements sodium and chlorine, which are 
combined in the proportion of their combining weights. 
The symbol of the compound is NaOl, which means a com- 
pound of the elements sodium and chlorine in the propor- 
tion 23 of sodium and 35.5 of chlorine. 

How Chemists Express Chemical Reactions.— The symbols 
are of great convenience when it is desired to express what 
has taken place in a chemical reaction. Thus you have 
seen that when the compound mercury oxide, HgO, is 
heated, it is decomposed into mercury and oxygen, a fact 
which is clearly expressed by the equation 






HgO-Hg + O, 

which tells not only the fact that decomposition takes place 
but the proportions by weight in which the substances take 
part. Thus, the compound, HgO, contains the elements in 
the proportion of 200 parts of mercury to 16 parts of 
oxygen. When 216 parts of this compound are decom- 
posed 200 parts of mercury and 16 parts of oxygen are 
obtained. 

A Chemical Problem. — Suppose you wished to know how 
much oxygen is contained in 50 grams of mercury oxide, 
how could you determine it? You know that in 216 parts 
of the compound there are 16 parts of oxygen; or, that in 
216 grams of the compound there are 16 grams of oxygen. 
How many grams of oxygen are there in 50 grams of the 



COMBINING WEIGHTS. 35 

compound? Plainly the answer is given by solving the 
expression 

216 : 50 :: 16 : the number of grams of oxygen contained 
in 50 grams of the oxide. 

Law of Multiple Proportions. — Two elements frequently 
combine in more than one set of proportions. Thus, while 
ordinarily iron and sulphur combine in the proportion 56 
of iron to 32 of sulphur, they also combine in the propor- 
tion 56 of iron to 64 of sulphur. Tin combines with oxy- 
gen in two proportions, forming two distinct compounds. 
In one 118 parts of tin are combined with 16 parts of oxy- 
gen; in the other 118 parts of tin are combined with 32 
parts of oxygen. The elements potassium, chlorine, and 
oxygen combine in several proportions as represented here : 

Potassium 39 39 39 39 

Chlorine 35.5 35.5 35.5 35.5 

Oxygen 16 32 48 64 

It will be observed that while in the compounds men- 
tioned the quantities of oxygen and sulphur united with 
the same element or elements vary, these quantities are 
closely related to one another. In the case of iron and sul- 
phur there is twice as much sulphur, relatively, in one 
compound as in the other. So, also, in the compounds of 
tin and oxygen there is twice as much oxygen combined 
with a given quantity of tin in one case as in the other. 
Finally, in the four compounds which are made up of 
potassium, chlorine, and oxygen the quantity of oxygen 
varies, being twice as great in the second compound as in 
the first, three times as great in the third, and four times 
as great in the fourth. These facts, and others of the 
same kind, are summed up in the Law of Multiple Propor- 
tions, which may be stated thu&: 



36 THE ELEMENTS OF CHEMISTRY. 

If two elements, A and B, combine in different propor- 
tions, the relative quantities of B which combine with any 
fixed quantity of A bear a simple ratio to one another. 

Symbols of Compounds of Elements Combined in More than 
One Proportion. — As has already been stated, when two 
elements combine in the simplest proportion the symbol 
of the compound is made by putting the symbols of the 
elements side by side, as in HgO, NaCI, etc., etc. If it i 
desired to represent compounds of the same elements com- 
bined in different proportions, use is made of small figures 
placed below the line, as in the symbols S0 2 , C0 2 , H 2 S0 4 , 
etc., etc. The meaning of the figures is simply this : In 
the compound S0 2 sulphur and oxygen are combined in the 
proportion of the combining weight (32) of sulphur and 
twice the combining weight (16) of oxygen, or 32 parts of 
sulphur to 32 parts of oxygen, which happens to be the 
same as 1 part of one to 1 part of the other. The symbol 
H 2 S0 4 represents a compound made up of hydrogen, sul- 
phur, and oxygen in the proportion ttvice the combining 
weight of hydrogen (1), the combining weight of sulphur 
(32) and. four times the combining weight (16) of oxygen ; 
or 2 parts hydrogen, 32 parts sulphur, and 64 parts oxygen, 
making all together 98 parts of the compound. 

Problem. — How much sulphur is there in 60 grams of the com- 
pound H2SO4 (sulphuric acid) ? How much oxygen ? How much 
hydrogen ? 

ft f ,£,/ 

*/<r - 

ft, WYYYJV 



NITROGEN. 37 



CHAPTER V. 
NITROGEN. 

Occurrence of Nitrogen.— You have already learned that 
about four fifths of the bulk of the air is nitrogen. This 
element is also found in combination in a large number of 
substances in nature. It is found in the nitrates, as salt- 
petre or potassium nitrate, KN0 3 , and Chili saltpetre or 
sodium nitrate, JSTaN0 3 . It is also found in the form of 
ammonia, which is a compound of nitrogen and hydrogen 
of the formula NH 3 . Ammonia occurs in small quantity 
in the air, and is formed under a variety of conditions, 
which will be referred to when the substance is considered. 
Nitrogen occurs, further, in most animal substances in 
chemical combination. 

Preparation of Nitrogen. — The most convenient way to 
prepare nitrogen is to burn a piece of phosphorus in a bell- 
jar over water. The reasons why phosphorus is better for 
the purpose than most other substances are (1) because it 
burns, that is combines with oxygen, easily ; and (2) be- 
cause the compound which it forms with oxygen (the pro- 
duct of combustion) is a solid and dissolves in water. If 
the product of combustion were a gas this would remain 
mixed with the nitrogen after the combustion. 

Experiment 27. — Place a wide-mouthed jar over water in a 
larger vessel of water. In the middle of a fiat cork about three 
inches in diameter fasten a small porcelain crucible, and float 
this on the water in the trough. Put in it a piece of phosphorus 



38 THE ELEMENTS OF CHEMISEBY. 

about twice the size of a pea, and set fire to the phosphorus. 
Quickly place the jar over it on a support which will prevent the 
jar from sinking more than an inch or two in the water. At first 
some air will be driven out of the vessel on account of the expan- 
sion due to the heat. After the burning has stopped cover the 
mouth of the jar with a glass plate and turn it mouth upward. 
Try the effect of introducing successively several burning bodies 
into the nitrogen, as, for example, a candle, a piece of sulphur, 
phosphorus, etc. 

Other Substances besides Phosphorus maybe Used. —Any- 
thing that has the power to combine with oxygen may be 
used in the preparation of nitrogen from the air. Metallic 
copper is convenient, and is not unfrequently used. It is 
only necessary to pass air over heated copper, when the 
metal combines with oxygen, forming the solid copper ox- 
ide, CuO, leaving the nitrogen uncombined. 

Properties of Nitrogen. — You have seen that nitrogen is 
a colorless, tasteless, inodorous gas. It does not support 
combustion, nor does it burn. [Suppose nitrogen were 
combustible, what would be the composition of the atmos- 
phere ?] Nitrogen not only does not combine with oxygen 
readily, but it does not combine with any other element, 
easily except at a very high temperature, and then with only 
a few. Just as it does not support combustion, so also it 
does not support breathing. An animal would die in it, 
not on account of any active poisonous properties possessed 
by it, but for lack of oxygen. In the air it serves the use- 
ful purpose of diluting the oxygen. If the air consisted 
only of oxygen, all processes of combustion would certainly 
be much more active than they now are. What the effect 
on animals of the continued breathing of oxygen would be 
it is difficult to say, as but few experiments on this subject 
h&ve been made. 



NITBOGEN. 39 

Nitrogen and Oxygen are Mixed together, not Chemi- 
cally Combined in the Air. — It is not an easy matter to 
prove this statement satisfactorily, but the evidence is so 
strong that no chemist doubts it. 

(1) If nitrogen and oxygen are mixed together, the 
mixture acts just like air. When they are mixed there is 
nothing to show that chemical action takes place. You 
have seen that the combination of two substances gives rise 
to heat. When nitrogen and oxygen are mixed together 
there is no change in the temperature of the gases. 

(2) Substances known to be chemical compounds do not 
vary in composition; that of the air does vary slightly. 

(3) Air dissolves somewhat in water. If air which has 
been thus dissolved be pumped out and analyzed, it is 
found to have a composition different from that of ordinary 
air. Instead of containing 1 volume of oxygen to 4 vol- 
umes of nitrogen, it will contain 1 volume of oxygen to 
1.87 volumes of nitrogen. The relative quantity of oxygen 
is much larger in air which has been dissolved in water 
than in ordinary air. This is due to the fact that oxygen 
dissolves more readily in water than nitrogen does. If the 
gases were in chemical combination the compound would 
probably dissolve without changi of composition. 

Summary.- — The air consists of nitrogen and oxygen in 
the proportion of 4 volumes of the former to 1 volume of the 
latter. Oxygen supports combustion; nitrogen does not 
Oxygen supports respiration; nitrogen does not. Oxygen 
and nitrogen are elements. They are not chemically com- 
bined in the air. Oxygen is made by heating substances 
which contain it, as, for example, mercury oxide and po- 
tassium chlorate. Nitrogen is made by burning phos- 
phorus in a closed vessel containing air. 



40 THE ELEMENTS OF CHEMISTBY. 

Elements combine in definite proportions by weight 
(law of definite proportions). 

In each element a number may be selected by means of 
which the proportion by weight in which it enters into 
combination may be expressed (combining weights) 6 

If an element combines with another in more than one 
proportion, the quantities which enter into combination 
with a fixed quantity of the second element bear a simple 
ratio to one another (law of multiple proportions). 



WATER. 41 



CHAPTER VI 

WATER. 

Occurrence of Water in Nature. — The wide distribution 

of water on the earth is familiar to every one. But water 

also occurs in forms and conditions which prevent it from 

being easily recognized. Thus, all living things contain a 

large proportion of water, which can be driven off by heat. 

If a piece of wood or a piece of meat be heated, water 

passes off. 

Experiment 28. — In a dry tube heat gently a small piece of 
wood. What evidence do you obtain that water is given off ? Do 
the same thing with a piece of fresh meat. 

Large Proportion of Water in Animal and Vegetable 
Substances. — The proportion of water in animal and vege- 
table substances is very great. If the body of a man 
weighing 150 pounds were put into an oven and thorough- 
ly dried there would be left only about 50 pounds of solid 
matter, all the rest being water. As all meat, vegetables, 
and food-stuffs in general contain a similar large propor- 
tion of water, it is evident that water is an important arti- 
cle of commerce. When you buy four pounds of beef you 
pay for about three pounds of water and one pound of 
solid matter. 

Water of Crystallization. — Many chemical compounds 
when deposited from solutions in water often appear in 
regular forms called crystals. These frequently enclose 
w#ter in chemical combination, and this water is necessary 



42 THE ELEMENTS OF CHEMISTRY. 

in order that the substance may exist in the form of crys- 
tals. Water thus held in combination is called water of 
crystallization. 

Experiment 29. — Dissolve some ordinary alum in water (6-8 
ounces alum to 200 c.cm. water) by the aid of heat Filter 
through a plaited filter and allow the filtered solution to cool. 
Crystals of alum will be deposited. Pour off the liquid above 
and place a few of the crystals on a piece of dry filter-paper. 
After the water is all absorbed from them and they appear dry, 
put them in a dry test-tube and heat gently. What evidence 
have you that water is contained in the crystals ? 

Experiment 30.— Perform a similar experiment with some 
gypsum, which is the natural substance from which ' ' plaster of 
Paris' ' is made. 

Experiment 31. — Heat a few small crystals of copper sulphate 
or " blue vitriol." In this case the loss of water is accompanied 
by a loss of color. After all the water is driven off, the powder 
left behind is white. On dissolving it in water, however, the so- 
lution will be seen to be blue ; and if this solution be evaporated 
until the substance is deposited, it will appear in the form of blue 
crystals. 

Efflorescent and Deliquescent Substances. — Some sub- 
stances which contain water of crystallization give it up 
very easily when exposed to the air. Such substances are 
called efflorescent. 

Experiment 32. — Select a few crystals of sodium sulphate or 
Glauber's salt which have not lost their lustre. Put them on a 
watch-glass, and let them lie exposed to the air for an hour or 
two. They soon lose their lustre, and become white and powdery 
on the surface. 

Some compounds if deprived of their water of crystalli- 
zation will take it up again when allowed to lie in an 
atmosphere containing moisture. Such substances are 
called deliquescent. As the air always contains moisture, 
it is only necessary to expose such compounds to the air 
in order to notice the change. It is well shown by the 






WATER. 43 

compound calcium chloride, Ca01 2 . This substance has a 

remarkable power of attracting water and holding it in 

combination. 

Experiment 33. — Expose a few pieces of calcium chloride to 
the air. Its surface will soon give evidence of being moist, and 
after a time the substance will dissolve in the water which is ab- 
sorbed. 

Water is a Compound. — That water is a compound and 

not an element can be shown by passing an electric current 

through it. If the ends of the wires connected with a 

galvanic battery be put in water a short distance apart it 

will be noticed that bubbles of gas rise from each wire. 

As these gases cannot well come from the wires, the most 

probable supposition is that they are formed from the 

water. 

Experiment 34. — To the ends of the copper wires connected 
with two cells of a Bunsen's or Grove's battery fasten small plati- 
num plates,, say 25 mm. (1 inch) long by 12 mm. (■§■ inch) wide. 
Insert these platinum ends into water contained in a shallow 
glass vessel about 15 cm. (6 inches) wide and 7 to 8 cm. (3 inches) 
deep, taking care to keep them separated from each other. ISTo 
action will take place, for the reason that water will not conduct 
the current, and hence when the platinum ends are kept apart 
there is no current. By adding to the water one tenth its own 
volume of strong sulphuric acid it acquires the power to conduct 
the current. It will then be observed that bubbles rise from each 
of the platinum plates. In order to collect the gases the ap- 
paratus may be arranged as shown in Fig. 11. A and B repre- 
sent glass tubes which may conveniently be about 30 cm. (1 
foot) long and 25 mm. (1 inch) internal diameter. They should be 
marked by means of a file, or by etching, so that equal divisions 
can be recognized. Tubes thus marked so that the divisions in- 
dicate cubic centimetres are most convenient, and are easily ob- 
tained of dealers in chemical apparatus. The tubes are first 
filled with the water containing one tenth its volume of sulphuric 
acid, and then placed with the mouth under water in the vessel 
C. The platinum plates are now brought beneath the inverted 



44 



THE ELEMENTS OF CHEMISTRY. 



tubes. The bubbles will rise in them and displace the water. 
Gradually the water will be completely forced out of one of the 
tubes, while the other is still half full of water. The substance 
which we have thus collected in each of the tubes is an invisible 
gas. After the first tube is full of gas, remove it by placing your 
thumb over the mouth. Turn it mouth upward, and at once ap- 
ply a lighted match to it. A flame will be noticed. The gas 




Fig. 11. 



burns. Is it air ? Is it oxygen ? Is it nitrogen ? In the mean 
time the second tube will have become filled with gas. Eemove 
the tube in the same way, and insert a thin piece of wood with a 
spark on the end. Does this gas act like oxygen ? The gas col- 
lected in the tube which first became filled is known as hydrogen, 
while the other is oxygen. 

What the Experiment Shows. — The experiment just 
performed shows that when an electric current is passed 
through water hydrogen and oxygen are obtained, and 
also that there is obtained twice as much hydrogen by 
bulk as oxygen. Whether these are the only elements con- 
tained in water can only be shown by further experiments. 
But it will be necessary first to learn something about hy- 
drogen. 



HYDB0GE2T. 45 



\A 

CHAPTER VII. 

HYDROGEN. 

Occurrence of Hydrogen. — Hydrogen is found in nature 
very widely distributed, and in large quantity. It forms 
one ninth the weight of water, and is contained in all the 
principal substances which enter into the composition of 
plants and animals. 

Preparation of Hydrogen. — It may be obtained 

(a) By decomposition of water by means of the electric 
current; 

(b) By decomposition of water by means of certain 
metals; 

(c) By the action of substances known as acids on metals. 
The first method has already been illustrated in Experi- 
ment 34. 

Experiment 35. — Throw a small piece of sodium* on water. 
While it is floating on the surface apply a lighted match to it. 
What takes place ? The flame is due to burning hydrogen, the 
flame beiug colored yellow by the presence of sodium, some of 
which also burns. 

Experiment 36. — Certain metals which do not decompose 
water at ordinary temperatures, or which decompose it slowly, 
decompose it easily at elevated temperatures. This is true of 
iron. If steam be passed through a tube containing pieces of 

* The metals sodium and potassium are kept under kerosene oil. 
When a small piece is wanted, take out one of the larger pieces 
from the bottle, roughly wipe off the oil with filter-paper, and cut off 
a piece the size needed. It is not advisable to use a piece larger than 
a pea. 



46 



THE ELEMENTS OF CHEMISTRY. 






iron turnings or fine bright iron wire heated to redness, the 
water is decomposed, the oxygen is retained by the iron in chem- 
ical combination, while the hydrogen is liberated. In this ex- 
periment a porcelain tube with an internal diameter of from 20 
to 25 mm. (about an inch) and a gas-furnace are desirable, 
though a hard glass tube and a charcoal-furnace will answer. 
The arrangement of the apparatus is shown in Fig. 12. 




Fig. 12. 



Water-gas. — Many other substances have the power to 
decompose water and set hydrogen free. The fact that a 
combustible gas can be obtained from water has led to 
many attempts to manufacture gas for heating and illu- 
minating purposes from water. There is, however, no 
cheap substance which has the power to decompose water 
at ordinary temperatures. Heat must be used, and it is 
generally the case that the quantity of heat required to 
effect the decomposition is greater than that which would 
be obtained by burning the hydrogen formed. The so- 
called "water-gas" now r so extensively manufactured in the 
United States both for illuminating and heating is made 
by the action of highly heated hard coal on steam. The 
essential part of the chemical reaction is represented by 
the equation 

C + H 2 = CO -f 2H, 



HYDBOGEN-. 47 

Carbon (or coal) acting upon the water (H 2 0) combines 
with the oxygen, forming the compound carbon monoxide, 
CO, and leaving the hydrogen uncombined. Both pro- 
ducts are gases, and both burn; and when this mixture is 
enriched by some of the oils obtained from petroleum it 
burns well and gives a good light. 

The Common Acids. — Hydrogen is most conveniently 
made in the laboratory by treating a metal with an acid. 
As will be seen later, acids are substances which contain 
hydrogen, and which give up this hydrogen very easily and 
take up other elements in the place of it. Among the 
common acids found in every laboratory are hydrochloric 
acid, sulphuric acid, and nitric acid. These compounds 
will be considered in due time. 

Hydrogen is Generally Given off when a Metallic Ele- 
ment Acts upon an Acid.— This is shown as follows: 

Experiment 37. — In a cylinder or test-tube put some small 
pieces of granidated zinc, and pour upon it enough ordinary 
hydrochloric acid to cover it. What do you notice ? After the 
action has continued for a minute or two apply a lighted match 
to the mouth of the vessel. What takes place ? Try the same ex- 
periment with sulphuric acid diluted with six times its volume of 
water. * What is the result ? The gas given off is hydrogen. 
For the purpose of collecting it the operation is best performed in 
a bottle with two necks called a Wolff's flask (see Fig. 13), or in 
a wide-mouthed bottle in which is fitted a cork with two holes 
: (see Fig. 14). Through one of the holes passes a funnel-tube, 
and through the other a glass tube bent in a convenient form. 
Put a small handful of granulated zinc into the bottle and 

* If it is desired to dilute ordinary concentrated sulphuric acid 
with water, the acid should be poured slowly into the water while the 
mixture is constantly stirred. If the water is poured into the acid, 
the heat evolved at the places where the two come in contact may be 
Bo great as to convert the water into steam and cause the strong acid 
to spatter. 



48 



THE ELEMENTS OF CHEMISTRY. 



pour upon it enough of a cooled mixture of sulphuric acid and 
water (1 volume concentrated acid to 6 volumes of water) to cover 
it. Usually a brisk evolution of gas will take place at once. 
Wait two or three minutes, and then collect some of the gas 




Fig 13. 



Fig. 14. 



by displacement of water. Should the action become slow add a 
little more of the dilute acid. It will be well to fill several cylin- 
ders and bottles with the gas. 

Physical Properties of Hydrogen.— Hydrogen is a color- 
less, inodorous, tasteless gas. Made by the action of zinc 
on acids, it has a slightly disagreeable odor. This is due 
to the presence of small quantities of impurities. If these 
be removed the odor disappears. 

Experiment 38.— Pass some of the gas through a solution of 
potassium permanganate ; collect some of it, and notice whether 
it has an odor. The apparatus should be arranged as shown in 
Fig. 15. The solution of potassium permanganate is, of course, 
contained in the small cylinder, A, and the tubes so arranged that 
the gas bubbles through it. 

The gas is not poisonous, and may therefore be inhaled 



HYDBOGEW. 



49 



with impunity. We could not, however, live in an atmos- 
phere of hydrogen, as we must have oxygen. It is the 




Fig. 15. 



lightest substance known, being fourteen and a half times 
lighter than air and sixteen times lighter than oxygen. 

Experiment 39. — Place a vessel containing hydrogen with the 
mouth upward and uncovered. In a short time examine the gas 
and see whether it is hydrogen. 

Experiment 40. — Gradually bring a vessel containing hydro- 
gen with its mouth upward be- 
low an inverted vessel contain- 
ing air, in the way shown in Fig. 
16. The air will be displaced. 
On examination, the inverted ves- 
sel will be found to contain hydro- 
gen, while the one with the mouth 
upward will contain none. The 
gas is thus poured upward. Fig. 16. 

Experiment 41. — Soap-bubbles filled with hydrogen rise in the 




50 THE ELEMENTS OF CHEMISTRY. 






air. The experiment is best performed by connecting an ordi- 
nary clay pipe by means of a piece of rubber tubing with the 
exit-tube of a gasometer filled with hydrogen. Small balloons of 
collodion are also made for showing the lightness of ^hydrogen 
Large balloons are always filled with hydrogen or some other 
light gas. Some kinds of illuminating-gas are rich in hydrogen 
and may therefore be used for the purpose. 

Weight of Hydrogen Compared with that of Oxygen.— 

A litre of hydrogen at 0° 0. and under the pressure of the 
atmosphere weighs 0. 089578 gram. A litre of oxygen under 
the same conditions weighs 1.429 grams. These figures are 
to each other as 1 to 16. But the figures 1 and 16 are the 
combining weights of hydrogen and oxygen; that is to say> 
they are the figures best adapted to expressing the relative 
weights of these elements which enter into combination. 
A similar connection exists between the relative weights of 
equal volumes of some other elementary gases and their 
combining weights, as will be seen later. 

All Combining Weights are Referred to that of Hydro- 
gen. — The figures called the combining weights express 
the relations between the weights of the different elements 
which enter into combination. When we say that the 
combining weight of hydrogen is 1 and that of oxygen is 
16, we mean that the weight of oxygen which generally 
enters into combination is sixteen times as great as the 
weight of hydrogen which enters into combination. The 
figures 2 and 32 would express this relation just as well; so 
would 6 J- and 100; but the simplest figures which can be 
used are 1 for hydrogen and 16 for oxygen. Having 
adopted these, all other combining weights are referred ±o 
these. 

Hydrogen a Liquid. — At a very low temperature and 
high pressure hydrogen becomes liquid. 



HYDBOGEHT. 51 

Chemical Properties of Hydrogen. — Under ordinary cir- 
cumstances hydrogen is not a particularly active element. 
It does not unite with oxygen at ordinary temperatures, 
but, like wood and most other combustible substances, needs 
to be heated up to the kindling temperature before it will 
burn. You have seen that it burns if a lighted match be 
applied to it. The flame is colorless, or very slightly blue. 
As burned under ordinary circumstances the flame is col- 
ored, in consequence of the presence of foreign substances; 
but that it is colorless when the gas is burned alone can be 
shown by burning it from a platinum tube, which is itself 
not acted upon by the heat. 

Experiment 42. — If there is no small platinum tube available, 

roll up a small piece of platinum -foil and melt it into the end of 

a glass tube, as shown in Fig. 17. Connect the burner thus 

made with a bottle or gasometer 

containing hydrogen, and after || 

the gas has been allowed to issue mk 

from it for a moment * set fire to 1 |B 

it. In a short time it will be seen JW 

that the flame is practically color- F™^ Jw 

less and gives no light. That it ~~ 

Fig 17 
; is hot is shown by holding a piece 

! of platinum wire or a piece of some other metal in it. 

The Burning of Hydrogen. — Hydrogen burns. You have 

I already learned that burning consists in combining with 

! oxygen. On the other hand, substances which burn in the 

air are extinguished when put in a vessel containing hydro- 

' gen. This is the same as saying that a body which is com- 



* Always be cautious in working with hydrogen. The danger con- 
sists in the fact that a mixture of hydrogen and oxygen or hydrogen 
and air is extremely explosive. It requires a flame or spark to explode it. 
Always let the gas escape for a time, and collect a test-tube full and 
light to see if it will burn quietly, before applying a flame tp it. 



52 THE ELEMENTS OF CHEMISTRY. 

bining with oxygen does not continue to combine with 
oxygen when it is put in an atmos< 
phere of hydrogen, and does not com- 
bine with hydrogen. This is ex- 
pressed by saying that hydrogen does 
not support combustion. 

Experiment 43. — Hold a wide-mouthed 
bottle or cylinder filled with hydrogen with 
the mouth downward. Insert into the 
vessel a lighted taper held on a bent wire, 
as shown in Fig. 18. The gas takes fire 
at the mouth of the vessel, but the taper 
is extinguished. On withdrawing the 'ta- 
per and holding the wick for a moment in 
1 * the burning hydrogen, it will take fire, 

but on putting it back in the hydrogen it will be again extin- 
guished. Other burning substances should be tried in the same 
way. 




WATER. 



53 



CHAPTER VIII. 



WATER {Continued). 



Composition of Water. — In Chapter VI. you learned that 
hydrogen and oxygen are both set free when an electric 
current is passed through water. It remains to be seen 
whether these are the only elements contained in water. 
If water consists only of hydrogen and oxygen, then when 
these elements combine water should be formed. But 
when hydrogen burns it combines with oxygen. Is water 
formed when hydrogen burns ? 

Experiment 44. — Pass hydrogen from a generating-flask or a 
gasometer through a tube containing some substance that will 
absorb moisture, for all gases collected over water are charged 
with moisture. You have seen in Experiment 33 that calcium 




Fig. 19. 



chloride has the power to absorb moisture. It is extensively used 
in the laboratory for the purpose of drying gases, and it may be 
used in the present experiment. It should be in small pieces 



54 THE ELEMENTS OF CHEMISTBY. 

about the size of a pea, not powdered. After passing the hydr< 
gen through the calcium chloride, pass it through a tube ending 
in a narrow opening and set fire to it. (Take the precaution 
mentioned in the foot-note, page 51.) If now a dry vessel be held 
over the flame, drops of water will condense on its surface and 
run down. A convenient arrangement of the apparatus is shown 
in Fig. 19. A is the calcium chloride tube. Before lighting the 
jet hold a glass plate in the escaping gas, and see whether water is 
deposited on it. Light the jet before putting it under the bell- jar; 
otherwise, if hydrogen is allowed to escape into the vessel it will 
contain a mixture of air and hydrogen, and this mixture is explo- 
sive. 

Hydrogen and Oxygen do not Combine at the Ordinary 
Temperature. — If they did,, hydrogen would take fire the 
moment it comes in contact with the air. If we mix the 
gases together and allow the mixture to stand unmolested, 
it remains unchanged. If, however, we should bring a 
spark or a flame in contact with the mixture a violent ex- 
plosion would occur, and a careful examination would show 
that the explosion is caused by the combination of the two 
gases. The combination causes heat. The heat causes 
the gases to expand greatly and suddenly, and the noise is 
caused by this sudden expansion. The expansion is fol- 
lowed by a contraction. 

Experiment 45.- — Mix hydrogen and oxygen in the proportion 
of about 2 volumes of hydrogen to 1 volume of oxygen in a gas- 
ometer or large bottle. Fill soap-bubbles, made as directed in Ex 
periment 41, with this mixture and allow them to rise in the air. 
As each one rises bring a lighted taper in contact with it, when 
a sharp explosion will occur. Great care must be taken to keep 
all flames away from the vicinity of the vessel containing the mix- 
ture. 

Measuring the Volumes of Hydrogen and Oxygen which 
Combine to Form Water. — The last experiment simply 
showed that when a flame comes in contact with a mixture 



WATER. 55 

of hydrogen and oxygon an explosion occurs. To show 
what else takes place the experiment mast be performed in 
a closed vessel. This experiment has been performed many 
times. As it would be difficult for you to repeat it you 
will have to be satisfied with a description of the apparatus 
used and a statement of the result obtained. A tube is 
used which is marked on the outside so that the volume of 
gases contained in it can be seen, and has two small plati- 
num wires passed through it at the closed end, c ^ 
nearly meeting inside and ending in loops out- 
side, as shown in Fig. 20. It is called a eudio- 
meter. It is filled with mercury and inverted in a 
trough containing mercury. A quantity of pure 
hydrogen is now passed up into the tube and its 
volume accurately measured. Then just half this 
volume of oxygen is introduced, and after the mix- 
ture has stood for a few minutes, so that the gases 
can become thoroughly mixed, an electric spark is 
passed between the wires inside the tube by con- 
necting the loops with the poles of a small Euhm- 
korff coil or with a Leyden jar. The explosion 
takes place noiselessly and with very little danger. 
If the interior of the tube was dry before the ex- 
plosion, it will be seen to be moist afterwards. The ^^ ^ 
liquid water which is formed occupies almost no space as 
compared with the space occupied by the two gases before 
combination. Now, if the experiment be performed with 
the two gases in different proportions, it will be found that 
only when they are mixed in the proportion of 2 volumes 
of hydrogen to 1 volume of oxygen do they completely 
disappear when exploded. If there is a larger proportion of 
hydrogen present, the excess is left over. If there is a 



66 THE ELEMENTS OF CHEMISTRY. 

larger proportion of oxygen present, the excess of oxygen is 
left over. Thus it is shown that when hydrogen and oxy- 
gen combine to form water, they do so in the proportion of 
2 volumes of hydrogen to 1 volume of oxygen. 

Formation of Water by Passing Hydrogen over Heated 
Oxides. — Water may be formed by passing hydrogen over a 
compound containing oxygen and heating. A convenient 
substance for the purpose is the compound of copper and 
oxygen known as copper oxide or black oxide of copper. 
It contains its elements in the proportion represented by 
the formula CuO. At ordinary temperature hydrogen 
does not act upon this substance. At a high temperature 
the hydrogen combines with the oxygen, forming water, 
and the copper is left behind as such. The reaction is 
represented thus : 

CuO + 2H = H 2 + Ou. 
Experiment 46. — Arrange an apparatus as shown in Fig. 21. 

o 




Fig. 21. 



A is a Wolff's flask for making hydrogen. To remove impurities 
the gas is passed through a solution of potassium permanganate 
contained in the wash-cylinder B. The cylinder C contains con- 
centrated sulphuric acid, and the U-shaped tube D contains gran- 
ulated calcium chloride, both of them serving to remove moisture 
from the gas. The pure dry hydrogen is now passed through the 
hard glass tube E y which contains a layer of copper oxide. After 
the apparatus is filled with hydrogen the burner under E is 



WATER. 57 

lighted, and the copper oxide heated to low redness. Soon mois- 
ture will be seen in the end of the tube and drops of water will 
collect in the vessel 67. 

How this Experiment Shows the Composition of Water. — 

The copper oxide loses its oxygen and of course loses 
weight. If, therefore, you should weigh the copper oxide 
before the experiment, and afterward the copper, and 
should also collect and weigh the water formed, you could 
from the figures obtained easily calculate the relative weight 
of oxygen contained in water, thus : 

Let . x = weight of tube -f copper oxide before the experiment; 

y = weight of tube + copper after the experiment. 
Then x — y = weight of oxygen taken from the copper oxide. 

The water formed is collected in a small tube containing 
calcium chloride. 

Let a = weight of calcium chloride tube before ; 

b = weight of calcium chloride tube after. 
Then b — a = weight of water formed. 

If the experiment is carefully performed, it will be found 

<£ y 

that — — - is very nearly equal to f, which means that by 

weight oxygen forms eight ninths of water. 

Oxidation and Reduction. — Any substance which like 
hydrogen has the power to abstract oxygen from com- 
pounds containing it is called a reducing agent. The pro- 
cess of abstracting oxygen from a compound is called re- 
duction. Reduction and oxidation arc opposite processes. 

Applications of the Heat Evolved by the Combination of 
Hydrogen and Oxygen, — The heat evolved when hydrogen 
combines with oxygen is very great, and it is utilized for 
various purposes. To burn hydrogen in the air is, as we 
have seen, a simple matter, but to burn it in oxygen re- 



58 THE ELEMENTS OF CHEMISTRY. 

quires a special apparatus to prevent the mixing of the 
gases before they reach the end of the tube where the com 
bustion takes place. The oxyhydrogen Mow-pipe answers 
this purpose. It is simply a tube with a smaller tube pass 
ing through it, as shown in Fig. 22. 




Fig. 22. 



The hydrogen is admitted through a and the oxygen 
through b. It will be seen that they come together only 
at the end of the tube. The hydrogen is first passed 
through and lighted; then the oxygen is passed through 
slowly, the pressure being increased until the flame ap- 
pears thin and straight. It gives very little light, but it is 
intensely hot. 

Experiment 47. — Hold in the flame of the oxyhydrogen blow- 
pipe successively a piece of iron wire, a piece of a steel watch 
spring, a piece of copper wire, a piece of zinc, a piece of platinum 
wire. 

The Oxyhydrogen Blow-pipe Used in Working Platinum.— 
The metal platinum is used for many purposes, particularly 
for making chemical apparatus. The vessels are made 
from molten platinum, and the metal is melted by means 
of the oxyhydrogen blow-pipe. 

The Lime-light or Drummond Light. — When the flame 
of the oxyhydrogen blow-pipe is made to strike against 
some substance which it cannot melt nor burn up, the 
substance becomes heated so high that it gives off intense 
light. The substance commonly used is quicklime. 



WATER 59 

Hence the light is generally called the lime-light. It is 
also known as the Drummond light. 

Experiment 48. — Cut a piece of lime of convenient size and 
shape, say an inch long by three quarters of an inch wide and the 
same thickness. Fix it in position so that the flame of the oxy- 
hydrogen blow-pipe will strike upon it. The light is very bright, 
but by no means as intense as the electric light. 

Properties of Water. — Though, as we know, water is 
widely distributed over the earth, we never find it perfectly 
pure. All natural waters contain foreign substances in 
solution. These substances are taken up from the air or 
from the earth. Pure water is tasteless and inodorous. 
In thin layers it is colorless, but in thick layers it is blue. 
This has been shown in the laboratory by filling a long tube 
with distilled water. When looked through it appears 
blue. The beautiful blue color of some mountain lakes is 
the natural color of pure water. 

On cooling water contracts until it reaches the tempera- 
ture of 4° C. At this point it has its maximum density. 
When cooled below 4° it expands, and the specific gravity 
of ice is somewhat less than that of water. Hence ice 
floats on water. 

Natural Waters. — The purest water found in nature is 
rain-water, particularly that which falls after it has rained 
for some time. That which first falls always contains im- 
purities from the air. As soon as the rain-water comes in 
contact with the earth and begins its course toward the 
sea it begins to take up various substances, according to 
the character of the soil with which it comes in contact. 
Mountain streams which flow over rocky beds, particularly 
beds of sandstone, which is very insoluble in water, contain 
exceptionally pure water. Streams which flow over lim^ 



60 THE ELEMENTS OF CHEMISTRY. 

stone dissolve some of the stone, and the water becomes 
''hard." The many varieties of mineral springs have 
their origin in the presence in the earth of certain sub- 
stances which are soluble in water. Common salt occurs 
in large quantities in different parts of the earth. As it is 
easily soluble in water, many streams contain it; and as all 
the streams find their way into the ocean, you see one 
reason why the water of the ocean is salt. 

Effervescent Waters are such as contain some gas, 
usually carbonic-acid gas, in solution and give up a part of 
it when placed in open vessels. 

Chalybeate Waters contain some compound of iron. 

Sulphur-water contains a compound of hydrogen and 
sulphur, called hydrogen sulphide or sulphuretted hydrogen 
(which see). 

Impure Waters. — As streams approach the habitations of 
man they are likely to become contaminated. The drain- 
age from the neighborhood of human dwellings is very apt 
to find its way into a near stream. This condition of things 
is most strikingly illustrated by the case of a large town 
situated on the banks of a river. It frequently happens 
that the water of the river is used for drinking purposes, 
and it also frequently happens that the water is contami- 
nated by drainage. Water when once contaminated by 
drainage tends to become pure again by contact with the 
air in consequence partly of the action of the oxygen. 
Hence river- water may become fit for use after having been 
impure. If it is to be used for drinking purposes, however, 
it is not well to rely too much upon this process of purifi- 
cation. 

Wells should not be dug too near dwellings and farm- 
houses, as the drainage may find its way into them beneath 



WATER. 



61 



the surface of the earth. This is a frequent source of 
danger, as some diseases are communicated from one person 
to another by means of contaminated drinking-water. 

Distillation. — Water may be purified by means of distil- 
lation. This consists in boiling the water, and then con- 
densing the vapor by passing it through a tube which is 
kept cool by surrounding it with cold water. By means of 
distillation most substances in solution in water can be 
got rid of. Substances which are volatile, however, will 
of course pass over with the water vapor. Aboard ship salt 
water is distilled and thus made fit for drinking. In chem- 
ical laboratories ordinary water is distilled in order to purify 
it for fine work with chemical substances. A simple ap- 
paratus to illustrate the process of distillation is that shown 
in Fig. 23. 




Fig. 23. 

The water to be distilled is placed in the flask A. The 
flask is connected by means of a bent glass tube B with the 
long tube CC. This in turn is surrounded by the larger 
tube or jacket D. The side tube E is connected with a 
faucet by means of the rubber tube G. The water is 
allowed to flow slowly into the jacket and out at F> whence 



62 THE ELEMENTS OF GHEM18TRT. 






it passes through the rubber tube H to the sink. When 
the water in A is boiled, the vapor passes into the tube CC. 
Here it is cooled down, and takes the form of liquid, which 
runs down and collects in the flask K called the receiver. 
The apparatus therefore consists of three parts : the distil- 
liiig-jlask, the condenser, and the receiver. 

Experiment 49. — Dissolve some copper sulphate, or some other 
colored substance, in a litre of water, and distil the water. 

Uses of Water in Chemistry. — Water is the best solvent. 
A greater number of substances dissolve in it than in any- 
other liquid. Chemical operations are frequently carried 
on in solution. That is to say, the substances which are 
to act chemically upon one another are first brought into 
solution. The object of this is to get the substances into 
as close contact as possible. If we rub two solids together, 
the particles remain separated by sensible distances, no 
matter how finely the mixture may be powdered. If, how- 
ever, the substances be dissolved and the solutions poured 
together, the particles of the liquid move so freely among 
one another that they come in intimate contact, thus aiding 
chemical action. In some cases substances which do not 
act upon one another at all when brought together in dry 
condition act readily when brought together in solution 
(Experiments 8 and 9.) 

Solution. — In a solution the particles of the solid dis- 
solved are in some way attracted and held in combination 
by the particles of the liquid. There is a limit to the 
amount of any substance which can be held in solution at a 
given temperature. The substance dissolved is distributed 
uniformly through the solution, no matter how dilute or 
how concentrated the solution may be, provided it has stood 
long enough, or has been thoroughly mixed by stirring, 



WATEB. 63 

In representing by an equation a reaction which takes 
place between substances in solution, it is not customary to 
take account of the water which acts as a solvent. 

Summary. — You have thus learned that 

(1) Water can be decomposed into hydrogen and oxygen 
by means of an electric current; 

(2) The gases are obtained in the proportion of eight 
parts by weight of oxygen to one part by weight of hydro- 
gen, or one volume of oxygen to two volumes of hydrogen; 

(3) When hydrogen is burned water is formed; 

(4) When hydrogen and oxygen are mixed together they 
do not combine under ordinary circumstances; 

(5) When a spark or flame is brought in contact with 
the mixture, violent action accompanied by explosion takes 
place; 

(6) The action is caused by the chemical combination of 
the two gases; 

(7) They combine in the same proportions as those in 
which they are obtained from water by the action of the 
electric current; 

(8) Water can be made by passing hydrogen over heated 
copper oxide; 

(9) By weighing the copper oxide before and after the 
experiment, and determining the weight of the water 
formed, the proportion of water which consists of oxygen 
is found to be eight ninths. 

Formula of Water. — All the facts taken together prove 
that the composition of water is what it has been stated to 
be. Now, using the accepted combining weights of hydro- 
gen and oxygen, viz., 1 and 16, the simplest formula which 
expresses the composition of water is H 2 0. This expresses 
the fact that water is composed of 2 parts by weight of 



64 THE ELEMENTS OE CHEMISTS Y. 

hydrogen and 16 parts by weight of oxygen, or 1 part of 
the former to 8 parts of the latter. If 8' were adopted as 
the combining weight of oxygen the formula of water would 
be HO. 

Comparison of Hydrogen and Oxygen. — Hydrogen and 
oxygen are different kinds of matter, just as heat and elec- 
tricity are different kinds of energy. Heat can be con- 
verted into electricity, and electricity into heat, but one 
element cannot by any means known to us be converted 
into another. They appear to be entirely independent of 
each other. If we compare hydrogen with oxygen we find 
very few facts which indicate any analogy between the two 
elements. In their physical properties they are, to be sure, 
similar. Both are transparent, colorless, inodorous gases. 
On the other hand, oxygen combines readily with a large 
number of substances with which hydrogen does not com- 
bine. Oxygen, as you have seen, combines easily with car- 
bon, sulphur, phosphorus, and iron. It is a difficult matter 
to get any of these elements to combine directly with hy- 
drogen. Further, it is a general truth that substances 
which combine readily with hydrogen do not combine read- 
ily with oxygen. The two elements have opposite chemi 
cal properties. What one can do the other cannot do. 

Opposite Chemical Properties are Favorable to Combina- 
tion. — Not only do hydrogen and oxygen, with their oppo- 
site properties, combine with great ease under the proper 
conditions, but, as we shall see later, it is a general rule 
that elements of like properties do not readily combine 
with one another, while elements of unlike properties do 
readily combine with one another. 

Ozone. — When electric sparks are passed for a time 
through oxygen it is changed in a remarkable way. It ac- 



WATER 65 

quires a strong odor and is much more active than the 
substance which we call oxygen. The odor of the gas is 
noticed in the neighborhood of an electric machine in ac- 
tion, and is said to be noticed during thunder-storms. The 
substance which has the odor is ozone. It is formed in a 
number of chemical reactions, as when phosphorus acts on 
air in the presence of water. By cold and pressure it 
has been obtained in the form of a dark-blue liquid. Ozone 
is present in small quantities in the air. 

Relation between Oxygen and Ozone. — When a certain 
volume of oxygen is converted into ozone the volume of 
gas is decreased to two thirds. 

By heating ozone above 300° C. it is converted into ordi- 
nary oxygen, and its volume increased from two to three. 

It is clear that the element oxygen can be converted into 
something else without the addition of anything to it. 
This might lead you to think that it is not an element. 
But the substance formed from it has exactly the same 
weight and can be changed back to oxygen without any- 
thing being added to it. It follows that the change must 
take place within the oxygen itself. 

Hydrogen Dioxide, H 2 2 . — Besides water, hydrogen and 
oxygen form a second compound with each other. This is 
hydrogen dioxide, H 2 2O * It is prepared by treating ba- 
rium dioxide, Ba0 2 , with sulphuric acid. It is a liquid 
which decomposes easily into water and oxygen. The ease 
with which it gives up oxygen makes it a good oxidizing 
agent. It is now manufactured on a large scale, and is 
used in medicine. 

* The reason for writing this formula H 2 2 and not HO will he 
seen later. 



66 THE ELEMENTS OF CHEMISTRY. 



CHAPTER IX. 

COMPOUNDS OP NITROGEN WITH HYDROGEN AND 
OXYGEN. 

Destructive Distillation of Animal and Vegetable Sub- 
stances which Contain Nitrogen. — Whenever a compound 
containing carbon, hydrogen, and nitrogen is heated in a 
closed vessel, so that the air cannot reach it, and it cannot 
burn up, the nitrogen passes out of the compound, not as 
nitrogen, but in combination with hydrogen, as ammonia. 
Nearly all animal substances contain carbon, hydrogen, 
oxygen, and nitrogen, and many of them give off ammo- 
nia when heated in the way described. Heating in this 
way is called destructive distillation. Similarly, com- 
pounds containing carbon, oxygen, and hydrogen, even 
though they be thoroughly dry, when heated give off oxy- 
gen in combination with hydrogen as water (see Experi- 
ment 1). The coal which is used for making illuminating- 
gas contains some hydrogen and nitrogen in chemical com- 
bination, and when the coal is heated in a closed vessel 
ammonia is given off. 

Natural Decomposition of Animal and Vegetable Sub- 
stances which Contain Nitrogen. — The decay or slow nat- 
ural decomposition of r.nimal and vegetable substances ex- 
posed to the air is familiar to every one. It is caused by the 
action of hosts of minute living things (called microbes) act- 
ing together with the oxygen of the air. Some animal sub- 
stances give off ammonia when they decompose in the air. 






COMPOUNDS OF NITROGEN. 67 

When animal substances decompose under proper condi- 
tions either a nitrite or a nitrate is formed; the former is 
derived from nitrous acid, HN0 2 , the latter from nitric 
acid, HN0 3 . In some countries where the conditions are 
favorable to the process immense quantities of nitrates are 
found, chiefly potassium nitrate or saltpetre, KN0 3 , and 
sodium nitrate or Chili saltpetre, NaN0 3 , so called because 
it is found in Chili in large quantities. From the nitrates 
nitric acid can easily be obtained. 

How Compounds of Nitrogen are Made. — The principal 
compounds of nitrogen are those which it forms with hy- 
drogen and oxygen. They are made either from ammonia 
or nitric acid by methods which will be described. 

Ammonia, NH 3 . — The conditions under which ammonia 
is formed have been mentioned. The chief source at pres- 
ent is the "ammoniacal liquor" of the gas-works, which is 
the water through which the gas has been passed for the 
purpose of removing the ammonia. By adding hydro- 
chloric acid to this liquid ammonium chloride, commonly 
called sal ammoniac, is formed. This is the most common 
compound containing ammonia, and it is therefore used in 
the laboratory for making ammonia. 

Preparation of Ammonia. 

Experiment 50. — To a little ammonium chloride on a watch- 
glass add a few drops of a strong solution of caustic soda, and 
notice the odor of the gas given off. Do the same thing with 
caustic potash. Mix small quantities of quicklime and ammonium 
chloride in a mortar, and notice the odor. Has ammonium chlo- 
ride this odor ? 

To prepare ammonia mix slaked lime and ammonium 
chloride in the proportion of 2 parts of the former to 1 part 
of the latter, and gently heat the mixture. It has been 
shown that besides the ammonia, which is given off in the 



68 



THE ELEMENTS OF CHEMISTBY. 



form of gas, calcium chloride, CaCl 2 , and water are formed 
in the reaction. It is represented thus: 

2NH 4 01 + 0a0 2 H 2 = 2NH 3 + CaCl 2 + 2H 2 0. 
Experiment 51. — Arrange an apparatus as shown in Fig. 24. 




Fig. 24. 

In the flask put a mixture of 100 grams slaked lime and 50 grams 
ammonium chloride. Heat on a sand-bath. After the air is 
driven out, the gas will be completely absorbed by the water in 
the first Wolff's flask. Disconnect at A, and connect with another 
tube bent upward. Collect some of the escaping gas by displac- 
ing air, placing the vessel with the 'mouth downward, as the gas 
is much lighter than air. The arrangement is shown in Fig. 
25. The vessel in which the gas is collected 
should be dry, as water absorbs ammonia very 
readily. Hence also it cannot be collected over 
water. In the gas collected introduce a burning 
stick or taper. Does the gas burn? Does it 
support combustion ? In working with the gas 
great care must be taken to avoid breathing it in 
any quantity. After enough has been collected, 
connect the delivery- tube again with the series 
of Wolff's flasks, and pass the gas through the 
Fig. 25. water as long as it is given off. 

Properties of Ammonia. — Prom the observations made in 
the experiment just performed you see that ammonia is a 




COMPOUNDS OF NITROGEN. 69 

colorless, transparent gas. It has a very penetrating char- 
acteristic odor. In concentrated form it causes suffocation. 
It is but little more than half as heavy as air. It is easily 
compressed to the liquid form by pressure and cold. When 
the pressure is removed from the liquefied ammonia it 
passes back to the form of gas. In so doing it absorbs 
heat. These facts are taken advantage of for the artificial 
preparation of ice. Carre's ice-machine is used for this 
purpose. Ammonia does not burn in the air, but does burn 
in oxygen. It is absorbed by water in very large quantity. 
One volume of water at the ordinary temperature dissolves 
about 600 volumes of ammonia-gas, and at 0° C. about 1000 
volumes. 

Spirits of Hartshorn. — The solution of ammonia in water 
is what we commonly have to deal with under the name 
ammonia. In ordinary language it is called "spirits of 
hartshorn."" The solution loses all its gas when heated to 
the boiling temperature. 

Nitric Acid, HN0 3 . — To effect the direct union of nitro- 
gen with oxygen and hydrogen is not easier than to effect 
the direct union of nitrogen and hydrogen to form ammo- 
nia. The silent and continuous action of minute living 
things in the soil is always tending to transform the waste 
products of animal life into compounds closely related to 
nitric acid. In general, by oxidation the nitrogen of ani- 
mal substances is converted into nitric acid, while by re- 
duction it is converted into ammonia. 

Preparation of Nitric Acid. — Nitric acid is obtained from 
a nitrate like potassium nitrate, K]ST0 3 , or sodium nitrate, 
NaN"O s , by treating with sulphuric acid. 

2Na^0 3 + H 2 S0 4 = Na 2 S0 4 + 2HNO,. 

Sodium - sulphuric . sodium , nitric 

nitrate ana acid gl e sulphate ana acid. 



70 



THE ELEMENTS OF CHEMISTRY. 



You see that the hydrogen of the sulphuric acid changes 
place with the sodium of the nitrate. 
Experiment 52. — Arrange an apparatus as shown in Fig. 26. 




Fig. 26. 



In the retort put 25 grams sodium nitrate (Chili saltpetre) and 
1 5 grams concentrated sulphuric acid. On heating gently, nitric 
acid will distil over and be condensed in the receiver. In the 
latter stage of the operation the vessel becomes filled with a red- 
dish-brown gas. The acid which is collected has a somewhat 
yellowish color. 

Pure Nitric Acid is a colorless liquid. It gives off color- 
less fumes when exposed to the air. When boiled it under- 
goes slight decomposition into oxygen, water, and compounds 
of nitrogen and oxygen. One of these compounds is col- 
ored, and it is this which is noticed in the last experiment 
and whenever strong nitric acid is boiled. Nitric acid 
suffers a similar decomposition when exposed to the action 
of thD direct rays of the sun. In consequence of this de- 
composition bottles containing strong nitric acid sometimes 



COMPOUNDS OF NITBOGEN. 71 

contain a reddish-brown gas above the liquid after standing 
for some time. Strong nitric acid acts violently on many 
substances, particularly those of animal and vegetable 
origin, decomposing them. It causes bad wounds in con- 
tact with the flesh; it eats through clothing ; it burns 
wood; it dissolves metals; and it is altogether one of the 
most active of chemical substances. In working with it it 
is necessary to take the greatest care. 

Ordinary or Commercial Nitric Acid contains only about 
68 per cent of the chemical compound H1SJ~0 3 . The rest 
is mostly water, though there are several impurities present 
in small quantities. 

How to Make Strong Nitric Acid.*— Pure, strong nitric 
acid may be made by mixing commercial nitric acid and 
commercial strong sulphuric acid and distilling. 

Experiment 53. — Mix together 400 grams ordinary concen- 
trated sulphuric acid and 80 grams ordinary concentrated nitric 
acid. Distil the mixture from a retort arranged as in Experiment 
52, taking care to keep the neck of the retort cool by placing filter- 
paper moistened with cold water on it. Use the acid thus ob- 
tained for the purpose of studying the properties of pure nitric 
acid. 

Nitric Acid Gives up Oxygen Readily. — Nitric acid is 
much used on account of the ease with which it gives up 
oxygen. Many substances burn up in strong nitric acid. 

Experiment 54. — Pour concentrated nitric acid into a wide test- 
tube, so that it is about one fourth filled. Heat the end of a stick 
of charcoal of about the size of a lead-pencil, and, holding the 
other end with a forceps, introduce the heated end into the acid. 
It will continue to burn with a bright light, even though it be 

* The experiments with strong nitric acid may be performed or not 
as the teacher thinks best They had better not be performed by the 
pupils, and should not be performed by any one who is not experi- 
enced in working with chemical substances. 



72 



THE ELEMENTS OF CHEMISTBY. 



placed below the surface of the liquid. The action is oxidation. 
The charcoal in this case finds the oxygen in the acid and not in 
the air. Great care must be taken in performing this experiment. 
The charcoal should not come in contact with the sides of th 
test-tube. A large beaker-glass should be placed beneath tb 
test-tube, so that in case the tube should break, the acid woulc 
be caught and prevented from doing harm. The arrangement o: 
the apparatus is shown in Fig. 27. The gases given off from the 




Fig. 27. 



tube are offensive and poisonous. Hence this as well as all other 
experiments with strong nitric acid should be carried on either 
out of doors or under a hood in which the draught is good. 

Experiment 55. — In a small flask put a few pieces of granulated 
tin. Pour on this just enough strong nitric acid to cover it. 
Heat gently over a small flame. What takes place ? What is the 
appearance of the substance left in the flask ? It is mostly a com- 
pound of tin and oxygen. (See Experiment 7.) 

Action of Nitric Acid upon Some Metals. — Generally when 
an acid acts upon a metallic element like silver, copper, 
lead, etc., the hydrogen of the acid is liberated and the 
metallic element takes its place. Thus when nitric acid 



COMPOUNDS of nitbogen: 73 

acts upon silver the action takes place as represented in the 
equation 

Ag + HN0 3 = AgN0 3 + H. 

Silver and ■** give ^^ and hydrogen. 

The substances thus formed are called nitrates. At the 
same time the hydrogen and a part of the oxygen are taken 
out of the acid, and compounds of nitrogen and oxygen are 
formed which are represented by the formulas N0 2 , NO, 
and N 2 0. The first of these, nitrogen peroxide, N0 2 , is a 
colored gas, and as some of it is always formed when nitric 
acid acts upon metals in the air, the presence of the red- 
dish-brown gas observed in the experiments already per- 
formed with nitric acid will be readily understood. 

Experiment 56. — Dissolve a few pieces of copper-foil in ordi- 
nary commercial nitric acid diluted with about half its volume of 
water. The operation should be carried on in a good-sized flask 
and either out of doors or under a good hood. What action takes 
place ? After it is over what is the appearance of the liquid in 
the flask ? Pour it out and evaporate to crystallization. Com- 
pare the substance thus obtained with copper nitrate. — Heat 
specimens of each. — Treat small specimens with sulphuric acid.— 
Do the substances appear to be identical ? What reasons have 
you for considering them identical ? 

Aqua Regia is made by mixing together concentrated 
nitric and hydrochloric acid. It is an excellent solvent. 
It is called aqua regia because it dissolves the king of 
metals, gold. Similarly nitric acid is called aquafortis, or 
strong water. In olden times all liquids were regarded as 
kinds of water, and all gases as kinds of air. 

The Oxides of Nitrogen. — Nitrogen combines with oxygen 
in five proportions. The names and symbols of the com- 
pounds formed are here given. 



74 THE ELEMENTS OF CHEMISTRY. 

Nitrous oxide " N 2 

Nitric oxide , NO or N 2 2 

Nitrogen trioxide T$ 2 9 

Nitrogen peroxide N0 2 or N 2 4 

Nitrogen pentoxide N 2 6 

A Good Illustration of the Law of Multiple Proportions.— 

The combining weight of nitrogen being 14, the above sym- 
bols represent the fact that in the compounds of nitrogen 
and oxygen the quantities of . oxygen combined with 28 
parts of nitrogen are 16, 32, 48, 64, and 80 ; or 16, twice 
16, three times 16, four times 16, and 5 times 16 parts of 
oxygen are combined with 28 parts by weight of nitrogen 
This series of compounds is an excellent illustration of the 
law of multiple proportions, which is one of the most im 
portant and interesting truths of chemistry. — [What is the 
law of multiple proportions? How does this series illus- 
trate it?] 

Nitrous Oxide, N 2 0. — This compound is formed by reduc- 
tion of nitric acid when the acid acts upon metals under 
favorable conditions of concentration and temperature. It 
is usually prepared by heating ammonium nitrate. The 
decomposition takes place as represented, thus: 

NH 4 N0 3 = • N 2 + 2H 2 

A *Sto*T heated gives "S and ™ ter ' 
Experiment 57. — In a retort heat 10 to 15 grams crystallized 
ammonium nitrate until it has the appearance of boiling. Do not 
heat higher than is necessary to secure a regular evolution of gas.. 
Connect a wide rubber tube directly with the neck of the retort, 
and collect the gas over water, as in the case of oxygen. 

Properties of Nitrous Oxide. — It is colorless and transpar- 
ent and has a slightly sweetish taste. When inhaled it 
causes a kind of intoxication, which is apt to show itself 
in the form of hysterical laughing. Hence the gas is com- 



COMPOUNDS OF NimOGEN. 



75 



monly called laughing-gas. Inhaled in larger quantity it 

causes unconsciousness and insensibility to pain. It is 

therefore used in certain surgical operations, particularly in 

pulling teeth. It supports combustion almost as well as 

pure oxygen. 

Experiment 58. — Insert into it a piece of burning wood, a can 
die, and a small piece of phosphorus. 

Nitric Oxide, NO. — This gas, as has been stated, is 

formed when nitric acid acts upon some metals, as copper. 

It seems probable that two changes take place: 

(1) The copper displaces the hydrogen of the acid, and 
copper nitrate is formed; and 

(2) The hydrogen acts upon the nitric acid, reducing it 
and forming nitric oxide. 

These two stages may be represented thus: 

2HN0 3 + Ou = Cu(N0 3 ) Q + 2H; 

and copper give ^?2SL and hydrogen; 



Nitric 
acid 



2HN0 3 + 6H = 4H,0 + 2NO. 



and 



Nitric 
acid 



and hydrogen give water and 



nitric 
oxide. 






Experiment 59. — Arrange an apparatus as shown in Fig. 28. 
In the flask put a few pieces of copper-foil. Cover 
this with water. Now add slowly, waiting each 
time, ordinary concentrated nitric acid. When 
enough acid has been added gas will be given off. 
If the acid is added quickly it not infrequently 
happens that the evolution of gas takes place too 
rapidly, so that the liquid is forced out of the flask 
through the funnel-tube. This can be avoided by 
not being in a hurry. What is the color of the gas 
in the flask at first ? What is it after the action 
has continued for a short time ? Collect over 
water two or three vessels full. 

Properties of Nitric Oxide. — Nitric oxide is 

a colorless, transparent gas. Its most re- fig. 2& 




76 THE ELEMENTS OF CHEMISTRY. 

markable property is its power to combine directly with 
oxygen when the two are brought together. The reaction 
is represented by the equation 

NO + = NO, 2 . 

The product is nitrogen peroxide, and this at ordinary 
temperatures is a reddish-brown gas. 

Experiment 60. — Turn one of the vessels containing colorless 
nitric oxide with the mouth upward and uncover it. What takes 
place ? Explain the appearance of the colored gas in Experiment 
59, and the fact that it afterward disappeared. What was in the 
vessel at the beginning of the operation ? Bo not inhale the gas, 
Perform the experiment with nitric oxide where there is a good 
draught. 

Experiment 61. — Into one of the vessels containing nitric ox- 
ide insert a burning candle. Does the gas burn ? Does it sup- 
port combustion ? 

Nitric oxide does not burn and does not support com- 
bustion. 

Nitrogen Peroxide, N0 2 . — This is the reddish-brown gas 
formed in the experiments with nitric oxide. It has a dis- 
agreeable smell and is poisonous. It is used in large quan- 
tities in the manufacture of the extremely important sub- 
stance sulphuric acid, as will be explained farther on. 



CHLOBINE AND ITS COMPOUNDS. 77 



CHAPTEE X. 

CHLORINE AND ITS COMPOUNDS WITH HYDROGEN 
AND OXYGEN. 

Introductory. — A little later you will see that oxygen 
and nitrogen are members of families of elements. The 
other members of the oxygen family resemble oxygen in 
many respects, and the other members of the nitrogen 
family resemble nitrogen. Hydrogen, strange to say, does 
not belong to any family but stands by itself. Another 
family is the chlorine family, of which chlorine is the best- 
known member. 

Occurrence of Chlorine. — Chlorine, though widely dis- 
tributed in nature, does not occur in very large quantity as 
compared with oxygen and hydrogen. It is found chiefly 
in combination with the element sodium as common salt 
or sodium chloride, which is represented by the symbol 
NTaOl. It is also found in combination with other ele-= 
ments, as potassium, magnesium, etc. In small quantity 
it occurs in combination with silver, forming one of the 
most valuable silver ores. All the chlorine with which we 
have to deal is made from common salt. 

Preparation of Chlorine. — We cannot decompose sodium 
chloride directly into its elements. In order to get the 
chlorine out of the compound in the free state it is neces- 
sary first to get it in combination with hydrogen in the 
form of hydrochloric acid, HOI This is very easily ac- 



78 THE ELEMENTS OF CBEMISTKY. 

complished by treating salt with ordinary sulphuric acid« 
The reaction is represented thus: 

(1) 2NaCl + H 2 S0 4 = Na 2 S0 4 + 2HC1. 

Sodium OTw1 sulphuric _._ A sodium _, hydrochloric 
chloride and acid S lve sulphate and acid. 

As you see, the sodium of the salt and the hydrogen of 
the sulphuric acid exchange places, a kind of action which 
is very common. [How does the process for making nitric 
acid resemble this process?] Now, if hydrochloric acid be 
brought in contact with a substance which gives up oxygen 
easily, the hydrogen will unite with the oxygen to form 
water, and the chlorine will be set free. The reaction is 
represented thus: 

(2) 2HC1 + = H a O + 2a 

In the laboratory it is most convenient to bring together 
ordinary hydrochloric acid and manganese dioxide, Mn0 2 , 
a substance which you have already had to deal with in 
preparing oxygen. The action which takes place is repre- 
sented thus: 

Mn0 2 + 4HC1 = MnCl, + 2H a O + 201. 

Commercial Manufacture of Chlorine. — Chlorine is an im» 
portant article of commerce, as it finds extensive use for 
bleaching and disinfecting. As manganese dioxide is a 
comparatively expensive substance, efforts have been made 
to devise some cheaper method of preparation than that 
just mentioned. Two are in use. 

(1) Deacon's Process. — This consists in passing air and 
hydrochloric acid together through a heated tube contain- 
ing clay balls which have been saturated with a solution of 



CHLOBINE AND ITS COMPOUNDS. 



79 



copper sulphate or blue vitriol. Exactly why the oxida- 
tion should take place under these circumstances is not 
known. The main part of the action is the oxidation of 
the hydrochloric acid, as represented in equation (2) above. 
(2) Weldon's Process. — This consists, in the first place, 
in making the chlorine from manganese dioxide and hy- 




Fig. 29. 

drochloric acid, and then, instead of throwing away the 
liquid contained in the vessel, mainly manganese chloride, 
MnCl 2 , in solution, this is treated with steam, lime, and 
air, and thus converted into a substance which acts towards 
hydrochloric acid like manganese dioxide, setting chlorine 
free. 



80 THE ELEMENTS OF CHEMISTRY. 

Experiment 62. — In a flask put about 100 grams (3 to 4 
ounces) of black oxide of manganese. Pour upon it enough 
ordinary concentrated hydrochloric acid to cover it completely. 
Arrange the apparatus as shown in Fig. 29. Heat gently in a 
sand-bath, when chlorine will be given off. Collect six or eight 
dry cylinders or bottles full of chlorine by letting the delivery- 
tube extend to the bottom of the collecting vessel and covering 
the mouth of the vessel with a piece of paper. You can see when 
the vessel is full by the color of the gas. — The experimmts witl 
chlorine should be carried on in a place where the draught % 
good. Do not inhale the gas. 

(1) Into one of the vessels containing chlorine introduce a little 
finely powdered antimony. The two elements combine at once 
with evolution of light and heat. [In what respects does this ex- 
periment resemble the one in which iron was burned in oxygen t~ 

(2) Into a second vessel introduce a few pieces of heated cop- 
per-foil. Combination takes place with evolution of light and 
heat. A compound ot copper and cmorine is formed. 

(3) Into a third vessel introduce a piece of paper with writing 
on it, some flowers, and pieces of colored calico. Most of the 
colors will be destroyed if the substances are moist. 

(4) Into a fourth vessel introduce a dry piece of the same 
colored calico as that used in (3). The dry piece is not bleached; 
the moist piece is. 

Properties of Chlorine. — Chlorine is a greenish-yellow 
gas. It has a disagreeable smell, and acts upon the pas- 
sages of the throat and nose, causing irritation and inflam- 
mation. The feeling produced is much like that of "a 
cold in the head." Inhaled in concentrated form, that is, 
not diluted with a great deal of air, it would cause death. 
It is much heavier than air. Its specific gravity is 2.45. 
A. litre of chlorine gas at 0° C. and atmospheric pressure 
weighs 3.167 grams. It is soluble in water and acts upon 
mercury, and therefore must be collected by displacement 
of air. It combines readily with other substances and de* 
stroys colors or bleaches. It is one of the most active ele- 
ments. In bleaching it decomposes the colored substances 






CHLORINE AND ITS COMPOUNDS. 81 

and forms colorless substances. It is used to disinfect sub- 
stances. 

Disinfection. — Substances given off from persons sick 
with some diseases, such as typhoid fever, small-pox, etc., 
are apt to cause the same diseases in well persons. It is 
therefore desirable to destroy them. This is called disin- , 
fecting. One of the most valuable substances for this 
purpose is chlorine. It is sold in the form of "bleaching 
powder," known also as "chloride of lime," which is a 
compound made by passing chlorine gas into slaked lime. 
A solution of this substance in water is a valuable disin- 
fectant. Old drains, sinks, etc., from which bad odors 
arise may be purified by adding enough of such a solu- 
tion. 

Combination of Hydrogen and Chlorine. — Just as hydro- 
gen burns in the air it burns also in chlorine. 

Experiment 63. — Light a jet of hydrogen in the air and care- 
fully introduce it into a vessel containing chlorine. Does it con- 
tinue to burn ? What is the appearance of the flame ? What 
evidence have you that a product is formed ? Test the gas remain- 
ing in the jar with blue litmus solution shaken up in it, and com- 
pare with the action of chlorine-gas on the solution. 

The burning of hydrogen in air or oxygen is, as you 
have seen, simply the act of combination of hydrogen and 
oxygen, the product being water in the state of vapor, and 
therefore invisible. When hydrogen burns in chlorine the 
action consists in the union of the two gases, the product 
being hydrochloric acid, HC1, which forms clouds in the 
air. In both cases the action is accompanied by heat and 
light. 

Chlorides. — Just as the compounds of oxygen with other 
6 



82 THE ELEMENTS OF CHEMISTRY. 

elements are called oxides, so the compounds of chlorine 
with the elements are called chlorides. 

Hydrochloric Acid, HC1. — The only compound which 
chlorine and hydrogen form with each other is hydrochloric 
acid. It has already been shown that hydrogen burns in 
chlorine, and that hydrochloric acid is formed. The two 
gases may be mixed together and allowed to stand together 
indefinitely in the dark, and no action will ta"ke place. If, 
however, the mixture be put in a room lighted by the sun, 
but where the sun does not shine directly upon it, combina 
tion takes place gradually; and if the sun be allowed to 
shine upon the mixture for an instant, explosion occurs, 
and this is the sign of the combination of the two gases 
The same sudden combination is effected by applying a 
flame or spark to the mixture. In this case light causes 
chemical action. The art of photography depends upon the 
fact that light has the power to cause chemical changes, as 
will be more fully explained later. It should be specially 
noted that the cause of the chemical changes in the cases 
referred to is not the heat but the light. If the substances 
are heated to the same temperature in the dark, the 
changes do not take place. 

Preparation of Hydrochloric Acid. 

Experiment 64. — Pour 2 or 3 c. cm. concentrated sulphuric acid 
on a gram or two of common salt in a test-tube. What takes 
place ? Is a gas given off ? What is its appearance ? 



Hydrochloric acid is always made by treating common 
salt with sulphuric acid, when the reaction takes place which 
is represented in the equation 

SNaCl + H 2 S0 4 = Na 2 S0 4 + 2H01. 

The products are sodium sulphate and hydrochloric acid. 



CHLORINE AND ITS COMPOUNDS. 83 

The hydrochloric acid is given off as a gas, and the sodium 
sulphate remains behind in the flask. 

Experiment 65. — Arrange an apparatus as shown in Fig. 24, 
page 68. Weigh out, separately, 100 grams common salt, 100 
grams concentrated sulphuric acid, and 1 part water. Mix the 
acid and water, taking the usual precautions (see note p. 47). 
Let the mixture cool down to the ordinary temperature ; and 
then pour it on the salt in the flask. Now heat the flask gently, 
and the gas will be regularly given off. Conduct it at first 
through water contained in two or three Wolff's bottles until 
what passes over is completely absorbed in the first Wolff's bottle. 
The reason why gas at first bubbles through all the bottles is that 
the apparatus is full of air, which is first driven out. When the 
air has been displaced, the gas is all absorbed as soon as it comes 
in contact with the water. — After the gas has passed for ten to 
fifteen minutes disconnect at A (see Fig. 24). Notice the fumes. 
These become denser by ' ' blowing the breath" upon them. Apply 
a lighted match to the end of the tube. Does the gas burn ? 
Collect some of the gas in a dry cylinder by displacement of air, 
as in the case of chlorine. The specific gravity of the gas being 
1.26, the vessel must of course be placed with the mouth upward. 
Has the gas any color? Is it transparent? — Insert a burning 
stick or candle in the cylinder filled with the gas. Does the gas 
support combustion ? — Connect the generating-flask again with 
the bottles containing water, and let the process continue until no 
more gas comes over. The reaction represented in the equation 

2NaCl + H 2 S0 4 = Na 2 S0 4 + 2HC1 

is now complete. After the flask has cooled down pour water 
on the contents, and when the substance is dissolved filter it and 
evaporate to such a concentration that, on cooling, the sodium 
sulphate is deposited. Pour off the liquid, and dry the solid sub- 
stance by placing it upon folds of filter-paper. Compare the sub- 
stance with the common salt which you put in the flask before 
the experiment. What proofs have you that the two substances 
are not the same? Heat a small piece of each in a dry tube 
closed at one end. What differences do you notice ? — Treat a small 
piece of each in a test-tube with sulphuric acid. What difference 
<lo you notice? — If in the experiment you should recover all the 
sodium sulphate formed, how much would you have ? [The com- 



84 THE ELEMENTS OF CHEMISTRY. 

bining weight of sodium is 23; of sulphur 32; and of chlorine 
35.5.] The relations between the quantities of the substances 
which take part in the reaction are expressed as follows: 

2NaCl + H 2 S0 4 = NaaSO* 

2(23 +35.5) +2x1 + 32 + 4x16 2x23 + 32 + 4x16 



117 parts + 98 parts = 142 parts 

+ 2HC1. 

2(1 + 35.5). 



+ 73 parts. 

The quantity of sodium sulphate formed is to the quantity of 
sodium chloride as 142 is to 117. Therefore if you use 100 grams 
of sodium chloride, the quantity of sodium sulphate formed is 
found by solving the simple proportion 

117 : 100 :: 142 : grams of sodium sulphate. 

— Put about 50 c.cm. of the liquid from the first Wolff's bottle in 
a porcelain evaporating-dish. Heat over a small flame just to 
boiling. Is hydrochloric acid given off ? Can all the liquid be 
driven off by boiling ? — Try the action of the solution on some 
iron filings. Is a gas given off ? What is it ? — Add some to a 
little granulated zinc in a test-tube. Is hydrogen given off ? — 
Add some to a little manganese dioxide in a test-tube. Is chlo- 
rine given off ? — Add ten or twelve drops of the acid to 2 or 3 
c. cm. water in a test-tube. Taste the dilute solution. How would 
you describe the taste ? — Add a drop or two of a solution of blue 
litmus, or put into it a piece of paper colored blue with litmus. 
Litmus is a vegetable color prepared for use as a dye. Other 
vegetable colors are changed by hydrochloric acid. — The color will 
be restored by adding a few drops of caustic soda or ammonia. 

Composition of Hydrochloric Acid. — That hydrochloric 
acid consists of hydrogen and chlorine is shown by the fact 
that it is formed when hydrogen combines with chlorine. It 
has further been shown that when the two gases combine 
they do so in equal volumes, 1 volume of hydrogen com- 
bining with 1 volume of chlorine; and these 2 volumes form 
2 volumes of hydrochloric acid gas. In 36.5 parts by 



CHLORINE AND ITS COMPOUNDS. 85 

weight of hydrochloric-acid gas there are contained 1 part 
by weight of hydrogen and 35.5 parts by weight of chlorine. 
The combining weight of chlorine being 35.5, the composi- 
tion of hydrochloric acid gas is represented by the symbol 
HOI. 

Chemical Conduct of Hydrochloric Acid. — 1 . Hydrochlo- 
ric acid gives up its hydrogen when brought in contact 
with certain substances like iron, zinc, etc., which belong 
to the class called metals; and takes up these metallic ele- 
ments in place of the hydrogen. Thus zinc and hydro- 
chloric acid give zinc chloride and hydrogen: 

Zn + 2HC1 = ZnCl 2 + 2H. 

2. In contact with substances which give up oxygen, or 
with oxygen itself under certain, circumstances, it gives up 
its chlorine, while the hydrogen combines with oxygen to 
form water : 

2HC1 + = H 2 + 201. 

3. When it acts upon metallic oxides or compounds of 
the metals with oxygen, such as magnesia or magnesium 
oxide, MgO; lime or calcium oxide, CaO; zinc oxide, 
ZnO, etc., — compounds which do not easily give up their 
oxygen, — the hydrogen of the acid combines with the oxy- 
gen of the oxide to form water, while the metals combine 
with the chlorine: 

MgO + 2HC1 = MgCl 2 + H 2 0; 
CaO + 2HC1 = CaCl 2 + H 2 0; 
ZnO + 2HC1 = ZnCl 2 + H 2 0. 

Compounds of Chlorine with Oxygen and with Hydrogen 
and Oxygen.— As you have seen, chlorine combines very 



86 THE ELEMENTS OF CHEMISTRY. 

readily with hydrogen, and hydrogen with oxygen, and the 
products are stable compounds. On the other hand, chlor- 
ine does not combine directly with oxygen. Indirectly the 
two elements can be made to combine, but the compounds 
decompose very easily into the elements. 

Compounds of Chlorine with Hydrogen and Oxygen. — The 
principal reaction made use of for the preparation of com- 
pounds of chlorine, oxygen, and hydrogen consists in treat- 
ing caustic potash or potassium hydroxide, KOH, with 
chlorine. If the solution of caustic potash is warm and 
concentrated the reaction takes place mainly as represented 
in this equation: 

6KOH + 6C1 = 5KC1 + KC10 3 + 3H 2 0. 

The compound KC1 is potassium chloride ; K010 3 is the 
well-known substance potassium chlorate or chlorate of 
potash, used for making oxygen in Experiments 20 and 21. 

If the solution is dilute the reaction takes place thus : 

2KOH + 2C1 = KOI + KCIO + H 2 0. 

The product KCIO is known as potassium hypochlorite. 

Hypochlorous Acid, HCIO, and Chloric Acid, HC10 3 . — 
Just as sodium nitrate, ISTaNOg, yields nitric acid, HNO a , 
when treated with sulphuric acid (see Experiment 52); and 
sodium chloride, NaCl, yields hydrochloric acid, HOI (see 
Experiment 65); so potassium chlorate, KC10 3 , yields 
chloric acid, HC10 3 ; and potassium hypochlorite, KCIO, 
yields hypochlorous acid, HCIO: 

2NaN0 3 + H 2 S0 4 = 2HNO, + Na 2 S0 4 ; 
2Na01 + H 2 S0 4 = 2HC1 + Na 2 S0 4 ; . 
2KC10 3 + H 2 S0 4 = 2HC10 3 + K 2 S0 4 ; 
2KC10 + H 2 S0 4 = 2HC10 + K 2 S0 4 . 



CHLOBINE AND ITS COMPOUNDS. 87 

Bleaching-potvder or "chloride of lime" is a substance 
similar to potassium hypochlorite, and is formed by passing 
chlorine into slaked lime. It will be more fully considered 
under calcium. 

Other Compounds of Chlorine, Hydrogen, and Oxygen. — 
There are four compounds of chlorine, hydrogen, and oxy- 
gen. As far as composition is concerned, they bear a 
simple relation to one another. Beginning with hydro- 
chloric acid, we have a series of compounds the successive 
members of which differ by one combining weight of oxy- 
gen: 

Hydrochloric acid HC1. 

Hypochlorous acid . . HCIO. 

Chlorous acid HC10 2 . 

Chloric acid HC10 3 . 

Perchloric acid HC10 4 . 

This series, like the series of compounds of nitrogen and 
oxygen, illustrates very clearly the lata of multiple propor- 
tions. [What is the law of multiple proportions? In what 
way does this series illustrate the law ?] 

Compounds of Chlorine and Oxygen. — There are three of 
these compounds, viz. : chlorine monoxide, C1 2 0; chlorine 
trioxide, C1 2 3 ; and chlorine tetroxide, C10 2 (or C1 2 4 ). 
They are unstable substances which easily break up into 
chlorine and oxygen. They are not easily prepared in pure 
condition and are not well known. 



88 THE ELEMENTS OF CHEMISTRY. 



CHAPTEE XL 
ACIDS— BASES— NEUTBALIZATION— SALTS. 

Introduction. — You have already met with a number of 
substances called acids. It is now time to inquire what 
these substances haye in common which lead chemists to call 
them all acids. What is there in common, for example, be- 
tween the heavy, oily liquid sulphuric acid and the colorless 
gas hydrochloric acid? It is not possible to understand the 
nature of their common properties without reference to a 
class of substances to which special attention will be called 
in due time. These are the alkalies, which are the most 
marked members of a class of substances known as bases. 
Acids and bases have the power to destroy the characteristic 
properties of each other. When an acid is brought in con- 
tact with a base in proper proportions, the characteristic 
properties of both the acid and the base are destroyed. 
They are said to neutralize each other. 

A Study of Neutralization. — The most common acids are 
sulphuric, hydrochloric, and nitric acids. Among the 
more common bases are caustic soda, caustic potash, 
and lime. A convenient way to recognize whether a sub- 
stance has acid or basic properties is by means of certain 
color-changes. The dye litmus is blue. If a solution 
which is colored blue with litmus be treated with a drop or 
two of an acid, the color is changed to red. If now the 
red solution be treated with a few drops of a solution of $ 



A CIDS— BASES— NEUTBALIZA TION— SALTS. 



89 



base, the blue color is restored. There are many other 
substances which change markedly in color, according to 
whether the solutions in which they are present are acid or 
basic. An infusion of red cabbage, for example, changes 
color when treated with an acid, and recovers its color 
when again treated with an alkali. 

Experiment 66. — Make dilute solutions of nitric, hydrochloric, 
and sulphuric acids (1 part dilute acid, such as is used in the lab- 
oratory, to about 50 parts of water); and of caustic soda and 
caustic potash (about 5 grams to 100 c.cm. of water). Measure 
off about 20 c.cm. of each of the acid solutions. Add a few drops 
of a solution of blue litmus. Gradually add to each of the meas- 
ured quantities of acid sufficient dilute caustic soda to cause the 
red color just to change to blue. As long 
as the solution is red it is acid. When it 
turns blue it is alkaline. At the turning 
point it is neutral. The experiment is 
best performed with the aid of a burette 
which is a graduated tube with an open- 
ing from which small quantities can be 
poured. A convenient shape is that rep- 
resented in Fig. 30. At the lower end 
is a small opening. The flow of the 
liquid from the burette is controlled by 
means of a small pinch-cock. It will re- 
quire some practice to enable you to know 
exactly when the red color disappears and 
the blue appears, but with practice the 
point can be recognized with great accu- 
racy. Should too much alkali be allowed 
to get into the acid, add a small measured 
quantity of the acid from another burette. 
In one experiment neutralize 20 c.cm. of 
the acid; in a second 10 c.cm.; in a third 
'15 c.cm.— What relation do the quantities 
of alkali used bear to one another ?— Does it always require a 
definite quantity of alkali to neutralize a certain quantity of 
1 acid ? 




90 THE ELEMENTS OF CHEMISTRY. 

What is Formed when an Acid Neutralizes a Base ? — To 

determine this we may use in larger quantities the same 
substances as those used in the preceding experiments. 

Experiment 67. — (1) Dissolve 10 grams caustic soda in 100 cc. 
water. Add hydrochloric acid slowly, examining the solution 
from time to time by means of a piece of paper colored blue 
with litmus. As long as the solution is alkaline it will cause no 
change in the color of the paper. The instant it passes the point 
of neutralization it changes the color of the paper red. When 
this point is reached, evaporate the water on a water-bath to com- 
plete dryness, and see what is left. — Taste the substance. Has it 
an acid taste ? Does it suggest any familiar substance ? If it is 
common salt or sodium chloride, how ought it to conduct itself 
when treated with sulphuric acid ? Does it conduct itself in this 
way ? Is the substance an alkali ? Is it an acid ? Is it neutral ? 
Its formation took place according to the equation 

HC1 + JSTaOH = NaOl + H 2 0. 

2. Perform the same experiment, using nitric acid instead of 
hydrochloric acid. — Compare the product with sodium nitrate. 
Heat a small specimen of each in a tube closed at one end. What 
takes place ? Treat a small specimen of each with a little sul- 
phuric acid in test-tubes. What takes place? The reaction 
between nitric acid and caustic soda is represented thus: 

HN0 3 + NaOH = NaNO, + H 2 0. 

3. Similarly, sulphuric acid and caustic soda give sodium sul- 
phate and water, thus : 

H 2 S0 4 + 2NaOH = Na.SO* + 2H a O. 

4. Similar reactions take place with caustic potash. Hydro- 
chloric acid and caustic potash yield potassium chloride and water: 

HC1 + KOH==KCl+H 2 0. 

Nitric acid and caustic potash yield potassium nitrate and water ; 

HNOs + KOH = KN0 3 + H 2 0. 

Sulphuric acid and caustic potash yield potassium sulphate ancj 
water : 

H 3 S0 4 + 2KOH ==? K 2 S04 + 2HA 



ACIDS-BASES— NEUTEALIZATION— SALTS. 91 

What these Experiments Show. — Considering the facts 
just learned, you see 

(1) That an acid contains hydrogen; 

(2) That a base contains a metal; 

(3) That when an acid acts upon a base the hydrogen 
and the metal exchange places; 

(4) That the substance obtained from the acid by replac- 
ing the hydrogen by a metal is neutral; 

(5) That the substance formed by replacing the metal of 
the base by hydrogen is water. 

The Fourth Statement not General. — All these statements 
except the fourth hold true of all cases. In some cases 
after replacing the hydrogen of an acid by a metal the sub- 
stance has an alkaline reaction; and in other cases the pro- 
duct has an acid reaction. 

Products Formed when a Metal Acts upon an Acid. — You 
have already seen that hydrochloric acid and sulphuric acid 
act upon certain metals, as iron and zinc, and that the 
action consists in giving up hydrogen and taking up metal 
in its place. The products of this action are the same in 
character as those formed by the action of acids on 
bases. 

Acids, Bases, and Salts. — An acid is a substance contain- 
ing hydrogen, which it easily exchanges for a metal when 
treated with a metal itself, or with a compound of a metal 
called a base. 

A base is a substance containing a metal combined with 
hydrogen and oxygen. It easily exchanges its metal for 
hydrogen when treated with an acid. 

The products of the action of an acid on a base are, first, 
water, and, second, a neutral substance called a salt. In 
the examples already given, sodium chloride, potassium 



92 THE ELEMENTS OF CHEMISTRY. 

chloride, sodium nitrate, potassium nitrate, sodium sul- 
phate, and potassium sulphate are salts. 

What is a Metal ? — Unfortunately it is not an easy thing 
to give a satisfactory answer to this question.' We can give 
examples of metals, such as iron, zinc, silver, calcium, 
magnesium, etc.; but when we attempt to discover the 
common properties of these substances we are somewhat at 
a loss. In general, any element which has the power to 
enter into an acid in the place of the hydrogen is called a 
metal. With hydrogen and oxygen a metal forms a pro- 
duct which has the power to neutralize acids; that is to 
say, which has basic properties. 

Names of Acids. — The termination ic is generally used in 
naming acids, as is seen in the names hydrochloric, sul- 
phuric, nitric, etc. If a second acid containing the same 
elements exists and the proportion of oxygen contained in 
it is smaller than in the acid the name of which ends in tc, 
the second acid is given a name ending in ous. Thus, 
chlorous acid, H010 2 , contains a smaller proportion of 
oxygen than chloric acid, H010 3 . 

When more than two acids containing the same elements 
are known, prefixes are used to distinguish them. In the 
series of chlorine acids already referred to (see page 87), 
there is one acid which, so far as the proportion of oxygen 
contained in it is concerned, stands below chlorous acid. 
It is called A^ochlorous acid, the prefix hypo being derived 
from a Greek word meaning under. Further, there is an 
acid which contains a larger proportion of oxygen than 
chloric acid. It is called perchloric acid, the Latin prefix 
per meaning here very or fully. It will be seen that the 
names of the acids vary with the proportion of oxygen con- 
tained in them. 



ACIDS— BASES— NEUTRALIZATION— SALTS. 93 

Names of Bases. — As already stated, a base is a compound 
of a metal with hydrogen and oxygen. Thus caustic soda 
has the formula NaOH, caustic potash KOH, lime Ca0 2 H 2 , 
etc. They arc commonly known as hydroxides. To dis- 
tinguish between the hydroxides of the different metals, 
the names of the metals are put before the name hydroxide. 
Thus, caustic soda, ISTaOH, is called sodium hydroxide ; 
caustic potash, KOH, is called potassium "hydroxide ; 
caustic lime, Ca0 2 H 2 , is called calcium hydroxide, etc. 
These compounds are called hydrates by some chemists. 

Names of Salts.- — Every metal can form a salt with every 
acid. The salts derived from a given acid receive a general 
name, and this general name is qualified in each case by the 
name of the metal contained in the salt. Thus, all the salts 
derived from nitric acid are called nitrates ; all those de- 
rived from chloric acid are called chlorates; those derived 
from sulphuric acid are called sulphates. So too, further, 
the salts of chlorous acid are called chlorites; those of 
nitrous acid, nitrites; those of sulphurous acid, sulphites; 
etc., etc. You will notice that the last syllable of the name 
of the salt differs according to the name of the acid. If 
the name of the acid ends in ie, the name of the salt ends 
in ate. If the name of the acid ends in ous, the name of 
the salt ends in ite. To distinguish between the different 
salts of the same acid, the name of the metal contained in 
it is put before the general name of the salt. Thus, the 
potassium salt of nitric acid is called potassium nitrate, 
the sodium salt is called sodium nitrate ; the calcium salt 
of sulphuric acid is called calcium sulphate; the magnesium 
salt of nitrous acid is magnesium nitrite ; the calcium salt 
of hypochlorous acid is calcium hypochlorite, etc., etc. 

[Give the name and formula of the potassium salt of 






94 THE ELEMENTS OF CHEMISTRY. 

perchloric acid. — Give the name and formula of the sodium 
salt of hypochlorous acid. — Give the name and formula of 
the sodium salt of nitric acid.] 

Salts of Hydrochloric Acid. — If the salts of hydrochloric 
acid were named in accordance with the principle just ex- 
plained, they would be called TiydrocMorates. But these 
salts are identical with the products formed by direct com- 
bination of the metals with chlorine. Thus hydrochloric 
acid and zinc act as represented in the equation 

Zn + 2HC1 = ZnCl 2 + 2H; 

while zinc and chlorine act thus: 

Zn + 201 = Zn01 2 . . 

In each case the same product, ZnCl 2 , is formed. But 
these compounds of metals with chlorine are called chlo- 
rides, as has already been explained. Hence the name 
hydrochlorates is unnecessary. 

Acid Properties and Oxygen. — The observation that oxy- 
gen is generally present in acids led at one time to the be- 
lief that it is a necessary part of these substances. Hence 
the name oxygen, which means the acid-former, was given 
to it. That oxygen is not essential to the existence of acid 
properties is shown in the case of hydrochloric acid, and in 
a few other similar cases. It must be said, however, that 
the acid properties of substances are generally due to the 
presence of oxygen. Some substances with basic properties 
are converted into acids by causing them to combine with 
more oxygen. 



CARBON. 95 



CHAPTER XII. 
CARBON 

Carbon Found in All Living Things. — Wood, flesh, and 
other products of vegetable or animal life, when heated to 
a sufficiently high temperature "blacken, and afterwards, if 
they are heated in the air, they burn up, as we say. This 
blackening is due to the fact that the substances all con- 
tain carbon. When they are heated the other elements 
are first driven off in various forms of combination, while 
the carbon is the last to go. If they are heated in the air, 
the carbon finally combines with oxygen to form a colorless 
gas — it burns up. 

Destructive Distillation. — The process of heating sub- 
stances in closed vessels and collecting the products formed 
is called destructive distillation. Among the most inter- 
esting examples of destructive distillation are those of coal 
and of wood. Coal is heated, as already stated under Am- 
monia, for the purpose of making illuminating-gas. Wood 
is heated for the purpose of making charcoal. Many in- 
teresting and important substances are obtained in these 
processes. Some of them will be taken up farther on. 

Occurrence of Carbon. — From what has already been said 
you will see that the principal form in which carbon occurs 
in nature is in combination with other elements. It occurs 
not only in all living things, but in their fossil remains, as 



96 TEE ELEMENTS OF CHEMISTRY. 

in coal. Coal-oil on petroleum, the formation of which was 
in some way connected with the processes involved in the 
formation of coal, consists of a large number of compounds 
which contain only carbon and hydrogen. Most products 
of plant-life contain the elements carbon, hydrogen, and 
oxygen. Among the more common of these products are 
sugar, starch, cellulose, etc. Most products of animal life 
contain carbon, hydrogen, oxygen, and nitrogen. Among 
them may be mentioned albumin, fibrin, casein, etc. Car- 
bon occurs in the atmosphere in the form of carbon dioxide 
or carbonic acid. It also occurs in the form of salts of car- 
bonic acid, the carbonates, which are widely distributed, 
forming some large mountain-ranges. Limestone, marble, 
and chalk are calcium carbonate. 

Forms of the Element Carbon. — Uncombined, the element 
occurs pure in two very different forms in nature: (1) As 
diamond; and. (2) as graphite or plumbago. 

Diamond. — The celebrated diamond-beds are in the East 
Indies, Borneo, Sumatra, Brazil, Australia, Mexico, and 
the Cape of Good Hope. When found, diamonds are cov- 
ered with an untransparent layer, which must be removed 
before the beautiful properties appear. Diamond is the 
hardest substance known. Heated to a high temperature 
in oxygen, it burns up, forming only carbon dioxide. 

Graphite. — Graphite, or plumbago, is found in nature in 
large quantities. It can be prepared artificially by dissolv- 
ing charcoal in molten iron. From this solution it is de- 
posited as graphite on cooling. It has a grayish-black 
color and a metallic lustre. It is quite soft, leaving a 
leaden-gray mark on paper when drawn across it, and is 
hence used in the manufacture of so-called lead pencils. It 
is sometimes called black lead. Heated to a very high 



CABBON. 97 

temperature in the air, or in oxygen, it burns up, forming 
only carbon dioxide. 

Amorphous Carbon. — All forms of carbon which are not 
diamond, nor graphite, are included under the name amor- 
phous carton. This name means simply that it is not crys- 
tallized. 

How Charcoal is Made.— Charcoal is that form of carbon 
which is made by the charring process. This consists sim- 
ply in heating without a free supply of air. The substance 
almost exclusively used in the manufacture of charcoal is 
wood. Wood consists of a large number of substances, 
nearly all of which are made up of the three elements car- 
bon, hydrogen, and oxygen. When wood is burned in the 
air the products are carbon dioxide and water. If the air 
be prevented from coming freely in contact with the wood, 
the hydrogen is given off partly as water and partly in the 
form of volatile compounds containing carbon and oxygen. 
The carbon, however, is mainly left behind as charcoal, as 
there is not enough oxygen present to burn it. 

A Charcoal-kiln. — This consists essentially of a pile of 
wood so arranged as to leave spaces between the pieces. 
The pile is then covered either with mason-work or some 
rough material through which the air will not pass easily, 
as, for example, a mixture of powdered charcoal, turf, and 
earth. Small openings are left in the covering. The wood 
is kindled and burns slowly. After a time the holes 
through which the air gains access to the wood are closed 
up, and the process stops. Charcoal, which is impure 
amorphous carbon, is left behind. 

Properties of Charcoal. — Ordinary charcoal is a black, 
comparatively soft substance. It burns in the air, though 
7 



98 THE ELEMENTS OF CHEMISTRY. 

not easily, unless the gases which are formed are constantly 
removed and fresh air is supplied, as by blowing with a 
bellows. It burns readily in oxygen, as we have seen (Ex- 
periment 24). The product of the combustion in oxygen 
and in air, when there is no lack of oxygen, is carbon di- 
oxide, C0 2 . In the air when the draught is bad, another 
compound of carbon and oxygen, carbon monoxide, CO, is 
formed. 

Coke. — This is a form of amorphous carbon which is 
made by heating ordinary gas-coal without access of air, as 
is done on a large scale in the manufacture of illuminating- 
gas. Coke bears to coal about the same relation that char- 
coal bears to wood. 

Lamp-black is a very finely divided form of charcoal 
which is deposited on cool objects placed in the flames of 
burning oils. Most flames used for illuminating purposes 
give a black deposit of soot on objects placed in them. 
This soot is largely made up of fine particles of carbon. 
It is used in the manufacture of printer's ink. Carbon is 
acted upon directly by very few substances, and is insolu- 
ble, so that it is impossible to destroy the color of printer's 
ink without destroying the material upon which it is im- 
pressed. 

Bone-black, or Animal Charcoal, is a form of amorphous 
carbon which is made by charring bones and other ani- 
mal substances. Unless it is treated with an acid it con- 
tains the incombustible substances which form a part of 
bones. 

Charcoal-filters. — Bone-black and wood-charcoal are very 
porous and have the power to absorb gases. When placed 
in air containing bad-smelling gases, these are absorbed 






CARBON. 99 

and the air thus purified. When water which contains 
disagreeable substances is treated with charcoal, these are 
wholly or partly absorbed and the water improved. Char- 
coal-filters are therefore extensively used. A charcoal-fil- 
ter to be of value should be of good size, and from time to 
time the charcoal should be taken out and renewed. The 
small filters which are screwed into faucets are of little 
value, as the charcoal soon becomes charged with any ob- 
jectionable matter which may be present in the water. 

Bone-black Filters. — Some coloring matters are removed 
from liquids by passing the liquids through bone-black fil- 
ters. On the large scale, this fact is taken advantage of in 
the refining of sugar. The solution of sugar first obtained 
from the cane or beet is strongly colored; and if it were 
evaporated, the sugar deposited from it would be dark- 
colored. If, however, the solution be first passed through 
bone-black filters, the color is removed. 

Experiment 68. — Make a filter of bone-black by fitting a paper 
filter into a funnel 12 to 15 mm. (5 to 6 inches) in diameter at its 
mouth. Half fill this with bone-black. Pour a dilute solution 
of indigo* through the filter. If the conditions are right the so- 
lution will pass through colorless. — Do the same thing with a di- 
lute solution of litmus. — If the color is not completely removed 
by one filtering, filter the solutions again. — The color may also be 
removed from solutions by putting some bone-black into them 
and boiling for a time. Try this with half a litre each of the lit- 
mus and indigo solutions used in the first part of the experiment. 
Use about 4 to 5 grams bone-black in each case. Shake the solu- 
tions frequently while heating. 

Charring Prevents Decay. — Charcoal does not decay in 
the air or under water nearly as readily as wood. That is 

* Prepared by treating powdered indigo for some time with warm 
Concentrated sulphuric acid and diluting with much water. 



100 THE ELEMENTS OF CHEMISTRY. 

another way of stating the chemical fact that the substan- 
ces of which wood is made up are more susceptible to the 
action of other chemical substances than charcoal is. We 
have one illustration of this in the relative ease with which 
charcoal and wood burn in the air. Piles which are driven 
below the surface of water are charred to protect them 
from the action of those substances which cause decay. 

Coal. — Under this head are included a great many kinds 
of impure amorphous carbon which occur ready-formed in 
nature. Ordinarily coals are divided into hard and soft 
coals, or anthracite and bituminous coals. Then there are 
substances more closely related to wood and therefore 
called lignite, and those which represent a very early stage 
in the process of coal-formation, viz., peat. 

Formation of Coal. — A close examination of all these 
varieties has shown that they have been formed by the 
gradual decomposition of vegetable material where there 
was not free access of air. The process has been going on 
for ages. Sometimes the substances have been subjected to 
great pressure, as can be seen from the position in which 
they occur in the earth. 

Destructive Distillation of Coal. — All forms of coal con- 
tain other substances besides carbon. The soft coals are 
particularly rich in other substances. When heated they 
give off a mixture of gases and vapors of volatile liquids. 
The gases are, foj the most part, useful for illuminating 
purposes. The liquids form a black, tarry mass known as 
coal-tar, from which are obtained many valuable compounds 
of carbon. The gases are passed through water for the 
purpose of removing certain impurities. This water ab- 
sorbs ammonia and forms the ammoniacal liquor of the 
gas-works, 



CARBOK 101 

Diamond, Graphite, and Charcoal Different Forms of the 
Element Carbon. — An element, as you have learned, is a 
form of matter which cannot be decomposed into simpler 
substances by any means now known to chemists. From 
hydrogen we can get nothing but hydrogen, except by 
bringing it together with some other element; from nitro- 
gen we can get nothing but nitrogen, etc. In the case of 
carbon, however, it is possible for the element to appear in 
three forms, which differ markedly from one another. 
That they are the same substance, chemically speaking, 
can be proved by a sijnple experiment. If we were to burn 
the same weight of diamond, of graphite, and of charcoal, 
and collect and weigh the carbon dioxide formed in each 
case, we should find that the quantity of carbon dioxide 
formed is the same in each case. Further, knowing the 
composition of carbon dioxide, we know how much carbon 
is contained in a given weight of the gas. Calculating the 
quantity of carbon contained in the carbon dioxide ob 
tained in burning a piece of diamond, we should find that 
it is exactly equal to the weight of the diamond; and the 
same thing is true of graphite and charcoal. 

Problem. — How much carbon dioxide, C0 2 , should be ob- 
tained by burning 0. 5 gram diamond ? The combining weight of 
carbon is 12. 

Common Properties of the Different Forms of Carbon. — 

Notwithstanding the marked differences in their appear- 
ance the different forms of carbon have some properties in 
common. They are insoluble in all known liquids. They 
are tasteless, inodorous, and infusible. When heated with- 
out access of air, they remain unchanged unless the tem- 
perature is very high. 

Alloteopism. — That one and the same substance can ap- 



102 THE ELEMENTS OF CHEMISTBY. 

pear in markedly different forms under different conditions 
is seen in the case of water. Hail and snow would hardly 
be suspected of being the same substance by one not quite 
familiar with them. The difference in this case, as in that 
of carbon, is believed to be due to the way in which the 
small particles of which the substances are made up are 
arranged. If we had a number of small pieces of wood all 
of the same size and shape, say cubes, and should carefully 
arrange them in some regular way, we might easily make 
a comparatively compact mass of them., and the mass 
would have a regular form. We might, further, arrange 
them in some second way with regularity. And we might 
simply throw the pieces together in a jumble. These three 
kinds of arrangement would represent, in a rough way, the 
difference between the three forms of carbon. Each pile 
would be made of wood, but in outward appearance they 
would differ from one another. In a similar way oxygen 
and ozone differ from each other. The power which some 
elements have of existing in different conditions is called 
allotropism. 

Chemical Conduct of Carbon. — At ordinary tempera- 
tures carbon is an inactive element. If it be left in con- 
tact with any one of the elements thus far considered — 
viz., hydrogen, oxygen, chlorine, and nitrogen — no change 
takes place. At higher temperatures, however, it readily 
combines with other elements, especially oxygen. It com- 
bines with oxygen either directly, as when it burns in the 
air or oxygen; or it abstracts oxygen from some of the ox- 
ides. 

Direct Combination of Carbon with Oxygen. — This has 
been already shown in Experiment 24, and is familiar to 
every one in charcoal-fires. That carbon dioxide is tlie 



CARBON. 



103 



product formed may be shown by passing the gas into lime- 
water, when insoluble calcium carbonate will be thrown 
down. 

Experiment 69. — Put a small piece of charcoal in a piece of 
hard glass tube. Pass oxygen through the tube, at the same 
time heating it. Pass the gases into clear lime-water. Arrange 
the apparatus as shown in Fig. 31. A is a bottle containing 




Fig. 31. 



oxygen; B is the hard glass tube containing the charcoal; C is 
the cylinder with clear lime-water. The reason why lime-water 
is used is simply that an insoluble compound is formed, and this 
can be seen, and it can be separated from the liquid and exam- 
ined. The reaction which takes place is represented thus: 

Ca0 2 H 2 + C0 2 = CaC0 3 + H 2 0. 
Lime and «£g£ give ^*™ and water, 
(insoluble) 

No other common gas acts in this way with lime-water. Hence, 
when, under ordinary circumstances, a gas is passed into lime- 
water and an insoluble substance is formed, we may conclude that 
the gas is carbon dioxide. 



Carbon Abstracts Oxygen from Oxides. 

lustrated by the following experiments ; 



-This may be il- 



104 



TEE ELEMENTS OF CHEMISTRY. 




Fig. 32. 



Experiment 70.— Mix together 2 or 3 grams powdered coppre 
oxide, CuO, and about one tenth its weight of powdered charcoal; 

heat in a tube to which is fitted an 
outlet tube, as shown in Fig. 32. 
Pass the gas which is given off into 
clear lime-water contained in a test- 
tube.— Is it carbon dioxide ? What 
evidence have you that oxygen has 
been extracted from the copper ox- 
ide ? What is the appearance of the 
substance left in the tube ? Does it 
suggest the metal copper ? Treat a 
little with strong nitric acid. What 
should take place if the substance is 
metallic copper? (See Experiment 
56.) What does take place? The 
reaction between the charcoal and the copper oxide is represented 
thus: 

2CuO + C = 2Cu + C0 2 . 

Experiment 71.— Perform a similar experiment with a little 
white arsenic in a small glass tube closed at one end. Take 
about equal parts of charcoal and arsenic. White arsenic is a 
compound of the element arsenic and oxygen, As 2 3 . The re- 
action which takes place when it is heated with charcoal is repre- 
sented thus : 

2As 2 3 + 30 = 4As + 3C0 2 . 

The element arsenic is volatile, and is hence driven out of the 
bottom of the tube and deposited on the sides of the tube above 
the mixture in the form of a mirror with a metallic lustre. 

Use of Carbon (Charcoal) as a Reducing Agent.— As has 

already been explained, the abstraction of oxygen from a 
compound is known as reduction. Hence carbon is called 
a reducing agent. It is extensively used for the purpose of 
extracting metals from their ores, which are the forms in 
which they occur in nature. Thus, iron does not occur in 
nature as iron, but in combination with other elements, 
particularly oxygen. In order to get the metal the org 



CABBOF. 105 

must be reduced,, or, in other words, the oxygen must be 
extracted. This is invariably accomplished by heating it 
with some form of carbon, either charcoal or coke. 

[What other element which you have already studied 
acts as a reducing agent ? Give an example of its reducing 
power.] 



106 THE ELEMENTS OF CHEMISTRY. 



OHAPTEE XIII. 

COMPOUNDS OF CARBON WITH HYDROGEN; 
OXYGEN, AND WITH NITROGEN. 

Compounds of Carbon and Hydrogen. — In the laboratory 
it is not a simple matter to effect combination between car- 
bon and hydrogen except in a few simple cases. In nature 
processes are in operation which give rise to the formation 
of a. large number of compounds containing these elements; 
and, further, in the manufacture of illuminating-gas from 
coal the conditions are such as to cause the combination of 
carbon and hydrogen, several interesting compounds being 
thus formed. There are no other two elements which 
combine with each other in as many different proportions 
as carbon and hydrogen. The compounds thus formed are 
known as hydrocarbons. The number of hydrocarbons 
known is very great, being somewhere between one and two 
hundred. Fortunately, investigation has shown that quite 
simple relations exist between these compounds; and hence, 
though the number is large, the study is not as difficult as 
might be expected. 

Petroleum is an oily liquid found in many places in the 
earth in large quantity, particularly in Pennsylvania and 
the Caucasus. In the earth it contains both gases and liq- 
uids. When it is brought into the air, the pressure being 
removed, the gases are given off . There are several gas- 
eous hydrocarbons given off, and a large number of liquids 
left behind. 



COMPOUNDS OF CARBON 107 

Refining Petroleum. — The vapors from petroleum when 
mixed with air are explosive, and the thicker liquids clog 
the lamps and wicks. Therefore these must be removed 
before the oil is fit for household use. This is done by (1) 
distilling, (2) washing with sulphuric acid, (3) washing 
with alkali, and (4) washing with water. The product thus 
prepared is called kerosene. 

In refining petroleum a numbei of products are obtained 
which cannot be used in lamps. Those which are lighter 
than kerosene, that is to say those which boil at a lower 
temperature, are known as gasoline, naphtha, lenzine, etc. 
From the heavier portions, or those which boil at higher 
temperatures than kerosene, paraffin is made. Each o v f 
these substances is a mixture of several chemical com- 
pounds. 

Hydrocarbons contained in Petroleum. — The simplest 
hydrocarbon contained in petroleum is methane, or marsh- 
gas, CH 4 ; the next has the composition C 2 H 6 , the next 
C 3 H 8 , etc. It will be seen that these compounds bear a 
simple relation to one another, as far as composition is 
concerned. They are the first members of a series the 
names and symbols of the first eight members of which are 
given below: 

CH 4 , Methane, or Marsh-gas; 

2 H 6 , Ethane; 

C 3 H 8 , Propane; 

4 H 10 , Butane; 

C 5 H 12 , Pentane; 

C 6 H 14 , Hexane; 

C 7 H 16 , Heptane; 

8 H 18 , Octane. 



108 THE ELEMENTS OF CHEMISTRY. 

Homology.— -The first member of the series differs from 
the second by CH 2 ; there is also this same difference, in 
general, between any two consecutive members of the series, 
This relation is known as homology, and such a series as an 
homologous series. Carbon is distinguished from all other 
elements by its power to form homologous series. 

The Ethylene Series of Hydrocarbons. — Besides the series 
above mentioned which is known as the marsh-gas series, 
there are other homologous series of hydrocarbons. There 
is one beginning with ethylene, C 2 H 4 , examples of which 
are 

Ethylene, C 2 H 4 ; 
Propylene, C 3 H 6 ; 
Butylene, C 4 H 8 . 

The Acetylene Series. — There is a series beginning with 
acetylene, examples of which are 

Acetylene, C 2 H 2 ; 
Allylene, C 3 H 4 . 

The Benzene Series. — Another series begins with benzene, 
C 6 H 6 . Some of the members of this series are 

Benzene, 6 H 6 ; 
Toluene, 7 H 8 ; 
Xylene, 8 H 10 . 

Marsh-gas, Methane, Fire-damp, CH 4 . — Marsh-gas is 
found in nature in petroleum, and is given off when the 
oil is taken out of the earth. It is formed, as the name 
implies, in marshes, as the product of a reducing process. 
Vegetable matter is composed of carbon, hydrogen, and 
oxygen. When it undergoes decomposition in the air in a 



COMPOUNDS OF CABBON. 109 

free supply of oxygen, the final products are carbon dioxide 
and water. When the decomposition takes place without 
access of oxygen, as under water, marsh-gas, which is a re- 
duction product, is formed. It bears to carbon much the 
same relation that ammonia bears to nitrogen. 

Occurrence of Marsh-gas in Coal-mines. — Marsh-gas is 
met with in coal-mines, and is known to the miners as fire- 
damp. Mixed with air it is one of the causes of the terrible 
explosions which occur in coal-mines. 

Preparation of Marsh- gas. — Marsh-gas is most readily 
prepared In the laboratory by heating sodium acetate with 
caustic potash and quicklime. 

Experiment 72. — Mix 5 grains dry sodium acetate, 5 grams 
potassium hydroxide, and 7-J grams quicklime. Heat in a retort. 
Collect over water as in making nitrous oxide. Does the gas 
burn ? Does it give light in burning ? 

Properties of Marsh-gas. — Marsh-gas is a colorless, trans- 
parent, tasteless, inodorous gas slightly soluble in water. 
It burns, forming carbon dioxide and water. When mixed 
with air, the mixture explodes if a flame or spark comes in 
contact with it. 

Ethylene, Olefiant Gas, 2 H 4 .— This hydrocarbon is formed 
by heating a mixture of ordinary alcohol and concentrated 
sulphuric acid. It is a colorless gas which can be con- 
densed to a liquid. It burns with a luminous flame. 

Acetylene, C 2 H 2 . — Acetylene is formed when a current of 
hydrogen is passed between carbon poles which are incan- 
descent in consequence of the passage of a powerful elec- 
tric current. In this case carbon and hydrogen combine 
directly. It is formed also when the flame of an ordinary 
laboratory burner (Bunsen burner) ci strikes back, " or burns 
at the base without a free supply of air. Its odor is un- 
pleasant,, It burns with a luminous, smoky flame. 



110 THE ELEMENTS OF CHEMISTRY. 

The Manufacture of Illuminating-gas. — The gas which 
is used for lighting buildings is generally made from coal. 
For this purpose, as has been stated, the coal is heated in 
closed vessels. The products which are formed are first 
passed through a series of tubes which are kept cool. In 
these a thick black liquid, known as coal-tar , collects. 
Then the gaseous products are passed through water which i 
takes up ammonia. The gases which remain are treated 
with two or three other substances to remove impurities, 
and are then collected in large vessels called gasometers. 
One ton of gas-coal yields an average of 10,000 cubic feet 
of gas. 

Coal-tar. — Coal-tar contains a very large number of 
compounds, some of which are obtained from it by distil- 
lation. The first products which pass over contain the 
hydrocarbons of the benzene series, of which benzene itself 
is the principal one. 

Carbon Dioxide, C0 2 .— The principal compound of carbon 
and oxygen is carbon dioxide, C0 2 , commonly called car- 
bonic acid. 

Occurrence of Carbon Dioxide.— Under the head of The 
Atmosphere it was stated that this gas is always present in 
the air. It issues from the earth in many places, particu- 
larly in the neighborhood of volcanoes. Many mineral 
waters contain it in considerable quantity, as the waters of 
Pyrmont, Selters, and the Geyser Spring at Saratoga. In 
small quantity it is present in all natural waters. In com- 
bination with bases it occurs in enormous quantities, par- 
ticularly in the form of calcium carbonate, CaC0 3 , varie- 
ties of which are ordinary limestone, chalk, marble, and 
calc-spar. 

Natural Formation of Carbon Dioxide. — Carbon dioxide 



COMPOUNDS OF CARBON. 



Ill 




is constantly formed in many natural processes. Thus, all 
animals that breathe in the air give off carbon dioxide from 
their lungs. 

Experiment 73. — Blow through, some lime-water by means of 
an apparatus arranged as shown in Fig 33. What evidence have 
you that your lungs give off car- 
bon dioxide ? 

It has already been shown 
that carbon dioxide is formed 
in the combustion of charcoal 
and wood. In a similar way 
it can be shown that the gas 
is formed whenever any of our 
ordinary combustible materials 
are burned. From our fires 
as from our lungs, and from fig. 33. 

the lungs of all animals, then, carbon dioxide is constantly 
given off. Further, the natural processes of decay of 
both vegetable and animal matter tend to convert the 
carbon of this matter into carbon dioxide, and this is 
then spread through the air. The process of alcoholic 
fermentation, and some other like processes, also give rise to 
the formation of carbon dioxide. In all fruit-juices there 
is contained sugar. When the fruits ripen, fall off, and 
"decay, the sugar is changed to alcohol and carbon dioxide. 

Preparation of Carbpn Dioxide. — The easiest way to get 
carbon dioxide is to add an acid to a carbonate. When- 
ever any acid is added to any carbonate there is an evolu- 
tion of gas. 

Experiment 74. — In different test-tubes containing a little 
sodium carbonate add dilute hydrochloric, sulphuric, nitric, and 
acetic acids. — What takes place? Is a gas given off? Pass it 
through lime-water. Is it carbon dioxide ? — Perform the same 
experiment with small pieces of marble. What gas is given off $ 



112 



THE ELEMENTS OF CHEMISTRY. 



To prepare carbon dioxide in the laboratory, calcium 
carbonate in the form of marble, or limestone, and hydro- 
chloric acid are commonly used. The reaction is repre- 
sented thus : 

CaC0 3 + 2H01 = 0aCl 2 + C0 2 + H 2 o 

Calcium 
carbonate. 



[What is the substance Ca01 2 ?] 

Experiment 75. — Arrange an apparatus as shown in Fig. 34. 
In the flask put some pieces of marble, and pour ordinary hydro- 
chloric acid on it. Collect the gas by displace- 
ment of air, placing the vessel with the mouth up- 
ward. Fill several cylinders or bottles with the 
gas. — Into one introduce a lighted candle, and 
afterwards a burning stick. What takes place ? 
Into another put a live mouse. What takes place ? 
With another proceed as if pouring water from it. 
Pour the invisible gas upon the flame of a burning 
candle. Pour some of the gas from one vessel 
to another, and show that it has been trans- 
ferred. Balance a beaker on a good-sized scales, 
and pour carbon dioxide into it. If the balance 
is at all sensitive, the pan in which the beaker is 
Fig. 34. placed will go down. 

Properties of Carbon Dioxide. — From the observations 
you have just made you have learned that carbon dioxide 
is a colorless gas at the ordinary temperature ; that it is in- 
combustible and does not support combustion; and that it 
is heavier than the air. When subjected to a low temper- 
ature and high pressure it is converted into a liquid, and 
this can further be changed to a solid. It has a slightly 
acid taste and smell. 

Why Carbon Dioxide does not Burn. — It does not burn 
for the same reason that water does not ; because it already 




COMPOUNDS OF CABBON 113 

holds in combination all the oxygen it has the power to 
combine with. Before it can burn again it must first be 
decomposed. 

Carbon can do Chemical Work. — Carbon has the power 
to combine with oxygen, and in so doing a definite quan- 
tity of heat is given off. A pound of carbon represents a 
definite quantity of chemical energy, which we can get, 
first, in the form of heat, and then convert into other forms, 
as electricity, motion, etc. After the pound of carbon has 
been burned, the product no longer represents the energy 
the carbon did. Similarly, a body of water elevated ten 
or fifteen feet represents a certain quantity of energy which 
can be obtained by allowing the water to fall upon the 
paddles of a water-wheel connected with the machinery of 
a mill. After the water has fallen, however, it no longer 
has the power to do work, or it has no energy. In order 
that it may again do work it must again be lifted up. 

Soda-water. — Carbon dioxide dissolves in water, one 
volume of water dissolving about its own volume of the gas 
at the ordinary temperature. When the pressure is in- 
creased the water dissolves more gas; and when the pres- 
sure is removed the gas again escapes. The so-called 
" soda-water" is simply water charged with carbon dioxide 
under pressure. The escape of the gas, when the water is 
drawn, is familiar to every one. The carbon dioxide used 
in charging the water is usually made from a sodium salt 
of carbonic acid known as "bicarbonate of soda." 

Breathing. — It was stated above that carbon dioxide is 
given off from the lungs as it is from a fire, and the fact 
was shown by means of a simple experiment. It is a waste 
product of the processes going on in the animal body. 
Just as it cannot support combustion, so animals cannot 
8 



114 THE ELEMENTS OF CHEMISTRY. 



, 



breathe in it. It is not poisonous any more than water is; 
but it cannot supply the oxygen which is needed for breath- 
ing purposes. In it animals die of suffocation, as they do 
in water. Any considerable increase in the quantity of 
carbon dioxide in the air above that which is generally 
present is objectionable, because it decreases the propor- 
tion of oxygen in the air which is breathed. If pure car- 
bon dioxide be introduced into the air it has been shown 
that as much as 5 per cent may be present without causing 
injury to those who breathe it. 

Air in Badly Ventilated Rooms. — In a badly ventilated 
room in which a number of people are collected and lights 
are burning, it is well known that in a short time the air 
becomes foul, and bad effects, such as headache, drowsi- 
ness, etc., are felt by those in the room. These effects are 
caused, not by the carbon dioxide, but by other waste 
products which are given off from the lungs in the process 
of breathing. - The gases given off from the lungs consist 
of nitrogen, oxygen, carbon dioxide, and water-vapor. 
Besides these, however, there are many substances in a fine 
state of division which contain carbon, and are in a state 
of decomposition. These are poisonous, and are the chief 
cause of the bad effects experienced in breathing air which 
has become contaminated by the exhalations from the 
lungs. 

Carbon Dioxide in Old Wells. — As carbon dioxide is 
formed in the earth wherever an acid solution comes in 
contact with a carbonate, the gas is frequently given off 
from fissures in the earth. It is hence not infrequently 
found in old wells which have not been in use for some 
time, and deaths have been caused by descending these 
wells for the purpose of repairing them. It is a good plan 



COMPOUNDS OF CARBON 115 

to let down a lighted candle into such a well before ventur- 
ing to go down. If the candle burns, the air can be 
breathed without danger. 

Choke-damp. — Carbon dioxide is also frequently met 
with in mines, and is called choke-damp by the miners. 
The miners know that after an explosion caused by fire- 
damp there is danger of death from choke-damp. The 
reason is simple. "When fire-damp, or marsh-gas, explodes 
with air the carbon is converted into choke-damp, or car- 
bon dioxide, and the hydrogen into water. 

Carbon Dioxide the Food of Plants. — Plants live largely 
on the carbon dioxide contained in the air. They have the 
power with the aid of the sun's light to decompose the 
gas, and they then build up the complex compounds of car- 
bon which form their tissues, using for this purpose the 
carbon of the carbon dioxide which they have decomposed. 

Plants the Food of Animals. — Animals eat either the 
products of plant-life or other animals which get their 
food from the vegetable kingdom. The food of animals 
comes, then, either directly or indirectly from plants. The 
food taken into the animal body is partly changed into 
other substances which form the structure of the animal; 
and partly it is oxidized, thus serving to keep the tempera- 
ture of the body up to the necessary point. That part of 
the food which suffers oxidation in the body acts the same 
as fuel in a stove. It is burned up, producing heat, the 
carbon being converted into carbon dioxide which is given 
off from the lungs. 

Carbon Dioxide Returns to the Air. — From fires and 
living things carbon dioxide is returned to the air, where 
it again serves as food for plants. When the life-process 
stops in the animal or plant, decomposition begins; and 



116 THE ELEMENTS OF CHEMISTBY. 

the final result of this,, under ordinary circumstances, i 
the conversion of the carbon into dioxide. 

No Life Without the Sun.— Every living thing is depen- 
dent upon the decomposition of carbon dioxide by plants 
and this decomposition cannot be effected without the aid 
of the sun. If the sun should stop shining, soon all life 
would cease. As the heat of the sun acting upon the great 
bodies of water and on the air gives rise to the movements 
of water which are essential to the existence of the world 
as it is, so the action of the sun^s rays on carbon dioxide, 
in the presence of the delicate and inexplicable mechanism 
of the leaf of the plant, gives rise to those changes in the 
forms of combination of the element carbon which accom- 
pany the wonderful process of life. 

Carbonic Acid. — A solution of carbonic acid in water has 
a slightly acid reaction. The solution will act upon basic 
solutions and form salts. The composition of the sodium 
salt formed in this way is Na 2 C0 3 ; that of the potassium 
salt K 2 C0 3 , etc. These salts are plainly derived from an 
acid, H 2 00 3 , which is carbonic acid. It is probable that 
the acid is contained in the solution. of carbon dioxide in 
water. It is, however, so unstable that it breaks up into 
carbon 'dioxide and water : 

H 2 C0 s = C0 2 + H a 0. 

The Carbonates. — When carbon dioxide acts upon a base 
it forms a salt. Thus, when potassium hydroxide or cal- 
cium hydroxide is used, the action which takes place is 
represented thus : 

2KOH + CO, - K 2 00 3 + H 2 ; 
CaO 1 H, + CO 1 = CaCO i + H,0, 






COMPOUNDS OF CARBON. Ill 

Experiment 76. — Pass carbon dioxide into a solution of caustic 
potash until it will absorb no more. Add acid to some of the 
solution thus obtained, and convince yourself that the gas given 
off is carbon dioxide. Write the equations separating the re- 
actions which take place on passing the carbon dioxide into the 
caustic-potash solution, and on adding an acid to the solution. 
What evidence have you that the gas given off is carbon dioxide ? 

Experiment 77. — Pass carbon dioxide into 50 to 100 cc. clear 
lime-water. Filter off the white insoluble substance. Try the 
action of a little acid on it. What evidence have you that it is 
calcium carbonate ? How could you easily distinguish between 
lime-water and a solution of caustic potash ? 

Calcium Carbonate Dissolves in Water containing Carbon 
Dioxide. — If you continue to pass carbon dioxide into lime- 
water after the calcium carbonate has been formed, the 
carbonate dissolves, and the solution finally becomes clear. 
If this solution be heated, the carbon dioxide is driven off 
and the calcium carbonate is again thrown down. 

Experiment 78. — Pass carbon dioxide first through a little 
water to wash it, and then into 50 to 100 cc. clear lime-water. 
After the solution has become clear, heat it. 

Hard Water. — Natural waters which flow over limestone 
take up more or less calcium carbonate by virtue of the 
carbon dioxide which they absorb from the air. Such 
waters, which are called " hard waters/' are in the condi- 
tion of the solution of calcium carbonate above referred to. 
When heated, the calcium carbonate is deposited. This 
is frequently noticed in the deposits in boilers and other 
vessels in which water is boiled. This kind of hardness is 
called "temporary hardness/' to distinguish it from "per- 
manent hardness" which is not affected by boiling. 

Carbon Monoxide, CO. — This compound is formed when a 
substance containing carbon is burned in an insufficient 
supply of air, — as, for example, when the draught in a 



118 THE ELEMENTS OF CHEMISTRY. 

furnace is not strong enough to remove the products of 
combustion and supply fresh air. It can also be made by 
extracting oxygen from carbon dioxide. It is only neces- 
sary to pass the dioxide over heated carbon, when the reac- 
tion which is represented in the following equation takes 
place : 

CO, + = 200. 

Formation of Carbon Monoxide in Coal-fires. — The for- 
mation of carbon monoxide can be well observed in a hard- 
coal fixe in an open grate. The air has free access to the 
coal, and at the surface complete oxidation takes place. 
But that part of the carbon dioxide which is formed at the 
lower part of the grate is drawn up through the heated 
coal and is partly reduced to carbon monoxide. When the 
monoxide escapes from the upper part of the grate it 
again combines with oxygen, or burns, causing the char 
acteristic blue flame always noticed above a mass of burn- 
ing hard coal. 

Carbon Monoxide contained in Water-gas. — Water-gas, 
as has been stated under Hydrogen, is made by passing 
water- vapor over highly heated coal, when this reaction 
takes place : 

+ H 2 = 00 + 2H. 

The gas obtained is therefore a mixture hi carbon mon- 
oxide and hydrogen. Before use it is enriched by the ad- 
dition of hydrocarbons from petroleum. As carbon mon- 
oxide is poisonous, laws have been passed in some States 
prohibiting the use of water-gas. 

Preparation of Carbon Monoxide. — Carbon monoxide is 
most easily made by heating oxalic acid, C 2 H 2 0^, with 



COMPOUNDS OF CABBON. 119 

sulphuric acid. The change which takes place is repre- 
sented thus : 

C a H 2 4 = CO, + CO + H 2 0. 

Both carbon dioxide and monoxide are formed. Both 
are gases. In order to separate them the mixture is 
passed through a solution of caustic soda, which takes up 
the carbon dioxide [forming what ?] and allows the mon- 
oxide to pass. 

Experiment 79. — Put ten grams crystallized oxalic acid and 
50-60 grams concentrated sulphuric acid in an appropriate-sized 
flask. Connect with two Wolffs flasks containing caustic-soda 
solution. Heat the contents of the flask gently. Collect some of 
the gas over water. Set fire to the same, and notice the charac- 
teristic blue flame. 

Properties of Carbon Monoxide. — It is a colorless, taste- 
less, inodorous gas, insoluble in water. It burns with a 
pale blue flame, forming carbon dioxide. It is exceedingly 
poisonous when inhaled. Hence it is very important that 
it should not be allowed to escape into rooms occupied by 
human beings, 

Danger of Coal-stoves. — We not unfrequently hear of 
deaths caused by the gases from coal-stoves. The most 
dangerous gas given off from coal-stoves is probably carbon 
monoxide. A pan of smouldering charcoal gives off this 
gas, and the poisonous character of the gas is well known. 

Carbon Monoxide a Reducing Agent. — At high temper- 
atures carbon monoxide has a very strong attraction for 
oxygen, and is hence a good reducing agent. In the re- 
duction of iron from its ores the carbon monoxide formed 
in the blast-furnace plays an important part. 

Experiment 80. — Pass carbon monoxide over some heated 
copper oxide contained in a hard glass tube. Is the oxide re- 



120 THE ELEMENTS OF CHEMISTRY. 

duced ? How do you know ? Is carbon dioxide formed ? What 
evidence have you ? Was the carbon monoxide free of carbon 
dioxide ? If not, what evidence have you that carbon dioxide is 
formed in this experiment ? 

Illumination. — In all ordinary forms of illumination we 
are dependent upon flames for the light. Whether we use 
illuminating-gas, a lamp, or a candle, the light comes from 
a flame. In the first case, the gas is burned directly ; in 
the case of the lamp, the oil is first drawn up the wick, 
then converted into a gas, and this burns ; while, finally, 
in the case of the candle, the solid material of the candle 
is first melted, then drawn up the wick, converted into gas, 
and the gas burns, forming the flame. In each case we 
have, then, a burning gas, and this burning gas we call a 
flame. 

When Burning Gases are Cooled Down they are Extin- 
guished. — You have already learned that substances need 
to be raised to the kindling temperature, before they will 
burn. This statement is as true of gases as of other sub- 
stances. When a current of hydrogen is allowed to escape % 
into the air, or into oxygen, no action takes place unless it 
be heated up to the burning temperature, when it takes 
fire and continues to burn. If the gas be cooled down ever 
so slightly, it is extinguished. 

Experiment 81. — Light a Bunsen burner. Bring down upon 
the flame a piece of brass or iron wire gauze. There is no flame 
above the gauze. That the gas passes through unburned can be 
shown by applying a light just above the outlet of the burner and 
above the gau*e. The gas will take fire and burn. By simply 
passing through the thin wire gauze, then, the gas is cooled down 
below its burning temperature. Turn on a Bunsen burner. Do 
not light the gas. Hold a piece of w r ire gauze about one and a 
half to two inches above the outlet. Apply a lighted match 
above the gauze, when the gas will burn above the gauze, but not 
below it. 



COMPOUNDS OF CABBOK 



121 



The Safety-lamp. — The facts illustrated in the last experi- 
ments are utilized in the miner's safety-lamp. One of the 
dangers which the miner has to encounter 
is the occurrence of fire-damp, or meth- 
ane, CH 4 , which with air forms an explo- 
sive mixture. The explosion can only be 
brought about by contact of a flame with 
the mixture. In order to avoid the con- 
tact, the flame of the safety-lamp is sur- 
rounded by wire gauze, as shown in Fig. 
35. When a lamp of this kind is brought 
into a mixture of marsh-gas and air, it, of 
course, passes through the wire gauze and 
comes in contact with the flame. A small 
explosion occurs inside the gauze, but the 
flame inside cannot pass through. Hence 
no serious explosion takes place. The 
flickering of the flame, and the occurrence 
of small explosions inside the gauze, fur- 
nish the miner with the information that 
he is in danger. 

Causes of the Luminosity of Flames. — There are several 
causes which make flames give light. One is the presence 
of solid substances in the flame. If a piece of platinum 
wire be put in a hydrogen flame which gives practically no 
light the flame becomes luminous. This fact has also been 
shown by introducing a piece of lime into the hot, non- 
luminous flame of the oxyhydrogen blow-pipe. A similar 
cause makes ordinary gas-flames luminous. There are 
always present in these flames particles of unburned carbon, 
as is shown by putting a solid substance into the flames, 
when a layer of soot, which consists mainly of finely divided 




Fig. 35. 



122 THE ELEMENTS OF CHEMISTRY. 

carbon, is deposited on it. Again, the denser the gas the 
more light it gives. A candle on the top of a high moun- 
tain, as Mont Blanc, on which the experiment was per- 
formed, gives less light than the same candle does at the 
level of the sea. 

Cyanogen, C 2 lSr 2 . — Carbon does not combine with nitro- 
gen under ordinary circumstances. If, however, they are 
brought together at very high temperatures in the pres- 
ence of metals, they combine to form compounds known 
as cyanides. When refuse animal substances, such as 
blood, horns, claws, hair, wool, etc., are heated togeth- 
er with potassium carbonate and iron, a substance known 
as potassium ferrocy article, or yellow prussiate of potash, 
K 4 Fe0 6 N 6 + 3H 2 0, is formed. When this is simply heated 
it decomposes, yielding potassium cyanide, KCN". From 
the potassium compound it is not difficult to make mercury 
cyanide, Hg(CN) 2 . By heating mercury cyanide it breaks 
up, yielding mercury and cyanogen gas: 

Hg(CF) 2 = Hg + C 2 N 2 . 

[What analogy is there between this reaction and that 
which takes place when mercury oxide is heated?] 

Properties. — Cyanogen is a colorless gas, easily soluble in 
water and alcohol. It is extremely poisonous. 

Hydrocyanic Acid, Prussic Acid, HON. — This acid occurs 
in nature in combination with other substances, — in bitter 
almonds, the leaves of cherry, laurel, etc. It is prepared 
from potassium cyanide, just as hydrochloric acid is pre- 
pared from sodium chloride. The reaction is: 

2KCN + H a S0 4 = K 2 S0 4 + 2HCK 



COMPOUNDS OF CARBON 123 

Properties — Hydrocyanic acid is a volatile liquid. It 
has a very characteristic odor resembling that of bitter 
almonds. It is extremely poisonous. It dissolves in water 
in all proportions, and it is such a solution which is known 
as prussic acid. 

Other Compounds of Carbon. — That part of Chemistry 
which has to do with the compounds of carbon is commonly 
called Organic Chemistry. It is more convenient to con- 
sider this subject after the chemistry of the other common 
elements has been studied. The last part of this book will 
treat of some of the more common and better known com- 
pounds of carbon. 



124 THE ELEMENTS OF CHEMISTRY. 



CHAPTER XIV. 

ATOMIC THEORY — ATOMIC WEIGHTS — MOLECULAR 
WEIGHTS — VALENCE — CLASSIFICATION OF THE 
ELEMENTS. 

The Laws of Chemical Action. — You have learned that 
there are two laws always governing chemical combination. 
These are the laws of definite and multiple proportions. 
These laws are simply statements which sum up what has 
been found to be true in ail cases examined. They are 
statements of facts discovered by actual experiment. 

We may Know a Fact without Knowing its Cause. — It is 
one thing to know a general fact, and quite another to 
know the cause of the fact. We know that all bodies are 
attracted by the earth, and that they fall when thrown into 
the air. But we do not know why this is so. So, too, 
though we know that substances combine according to the 
laws of definite and multiple proportions, it does not neces- 
sarily follow that we know why they combine according to 
these laws. 

Hypothesis and Theory. — When a law has been discovered 
by careful study of the facts, the next thing to be done is 
to imagine d cause. We try to imagine a condition of 
things which, if it existed, would lead to the results discov- 
ered. If we succeed in imagining such a condition of 
things we suggest an hypothesis. If, now, we test this hy- 
pothesis in every way that suggests itself, and find that all 
facts discovered are in accordance with it, we then call it a 



ATOMIC THEORY-VALENCE. 125 

theory. An hypothesis is a guess in regard to the cause oi 
certain phenomena. A theory is an hypothesis which has 
been thoroughly tested, and which is applicable to a large 
number of related phenomena.* 

The Atomic Theory. — The atomic theory was suggested 
to account for the laws of definite and multiple proportions. 
The theory is simply this: 

That all kinds of matter are made up of indivisible par- 
ticles called atoms; and that the atoms of the different 
elements have different iveights. 

Now if, when substances act upon one another/ the 
action takes place between these atoms, and consists either 
in a union or separation of the atoms, then it is easy to 
understand why compounds are formed according to the law 
of definite and multiple proportions. If two elements whose 
atoms have weights which are to each other as 2 to 9 
combine so that one atom of the one combines with one 
atom of the other, then the compound which is formed 
will contain the elements in the proportion of 2 parts by 
weight of the one to 9 parts by weight of the other ele- 
ment. If they combine so that one atom of the first 
element combines with two atoms of the other, then the 
resulting compound will contain the elements in the pro- 
portion of 2 parts by weight of the one to 18 parts by 
weight of the other element. 

* Hypotheses and theories are of great value to science, if founded 
upon a thorough knowledge of the facts to which they relate. They 
become dangerous when used by those who are not familiar with the 
facts. The student who has not received a thorough scientific train- 
ing should remember that theories and hypotheses, to be of value, 
must be suggested, not by a superficial but by a thorough knowledge 
of the facts. 






126 TEE ELEMENTS OF GEEMISTBT. 

Atomic Weights. — The weights of the elements which 
have thus far been referred to as combining weights are, in 
accordance with the atomic theory, the relative weights of 
the atoms, or the atomic weights. The symbols of the 
elements represent atoms of the elements. Thus, H repre- 
sents an atom of hydrogen, an atom of oxygen, etc. As 
hydrogen enters into combination in smaller proportion 
than any other element, its combining weight or atomic 
weight is taken as the unit. When we say that the atomic 
weight of oxygen is 16, we mean simply that the atom of 
oxygen is 16 times heavier than that of hydrogen. 

Molecules. — As the symbols of the elements represent 
atoms, so the symbols of compounds represent combina- 
tions of atoms. The symbol of hydrochloric acid, HC1, 
represents, according to the theory, the smallest particle 
of this substance that can exist. It is made up of an atom 
of hydrogen and an atom of chlorine, which are combined 
chemically. The symbols HN0 3J , H 2 0, NH 3 are intended 
to represent the smallest particles of the compounds that 
can exist. The smallest particle of nitric acid consists of 
1 atom of nitrogen, 1 atom of hydrogen, and 3 atoms of 
oxygen. These smallest particles of compounds are called 
molecule*. The molecules are made up of atoms. The 
weight of a molecule is equal to the sum of the weights of 
the atoms of which it is composed. 

Avogadro's Law. — A careful study of the conduct of 
gases has led to the conclusion that equal volumes of all 
gases under the same conditions of temperature and pres- 
sure contain the same number of molecules. This is known 
as Avogadro's law. 

The Relative Weights of Molecules Determined by 
Weighing Gases. — If Avogadro's law is true, then by 



ATOMIC THEORY— VALENCE. 127 

weighing equal volumes of gaseous substances we can 
learn the relative weights of the molecules of these sub- 
stances. 

Atomic Weights Learned from Molecular Weights. — If 
we knew the molecular weight of all compounds we could 
easily determine the atomic weights of the elements. It 
would only be necessary to select the smallest quantity of 
an element which occurs in any of its compounds. Thus, 
for example, if we were to examine all known oxygen com- 
pounds that can be studied in the form of gas or vapor, 
we should find that the smallest quantity of oxygen found 
in any molecule is represented by 16. 

Valence. — The formulas of the compounds thus far con- 
sidered have all been determined by exactly the same 
methods. On comparing the formulas of the simplest 
hydrogen compounds of chlorine, oxygen, nitrogen, and 
carbon a curious difference is observed. The formulas are 

C1H, OH„ NH 3 , CH 4 . 

According to the atomic theory these expressions mean 
that the molecule of hydrochloric acid consists of 1 atom 
of chlorine combined with 1 atom of hydrogen; the mole- 
cule of water consists of 1 atom of oxygen combined with 
2 atoms of hydrogen; the molecule of ammonia of 1 atom 
of nitrogen and 3 atoms of hydrogen; and the molecule of 
marsh-gas of 1 atom of carbon and 4 atoms of hydrogen. 
It appears, therefore, that the atom of oxygen can hold in 
combination twice as many hydrogen atoms as the atom of 
chlorine can; that the atom of nitrogen can hold three 
times as many; and the atom of carbon four times as 
many. Other atoms differ from one another in the same 
way. 



128 THE ELEMENTS OF CHEMISTRY, 

That property of an element by virtue of which its atom 
can hold in combination a definite number of other atoms 
is called valence. 

Kinds of Elements. — The smallest power, as far as the 
number of other atoms which it can hold in combination is 
concerned, is that of the chlorine atom. As one chlorine 
atom can hold but one hydrogen atom in combination, so 
one hydrogen atom can hold but one chlorine atom. 
Either the hydrogen atom or the chlorine atom may be 
taken as an example of the simplest kind of atom. An 
element like hydrogen or chlorine is called a univalent 
element; an element like oxygen whose atom can hold two 
unit atoms in combination is called a Mvalent element; an 
element like nitrogen whose atom can hold three unit 
atoms in combination is called a trivalent element; and an 
element like carbon whose atom can hold four unit atoms 
in combination is called a quadrivalent element. Most 
elements belong to one or the other of these four classes. 

[Calcium forms with chlorine the compound CaCl 2 . 
What is the valence of calcium ? Potassium and sodium 
form chlorides of the formulas KC1 and NaCl respectively. 
What is the valence of these elements ? Sulphur forms 
with hydrogen a compound of the formula SH 2 . What is 
the valence of sulphur ?] 

Displacing Power of the Elements. — In the formation of 
salts you have seen that the hydrogen of acids is displaced 
by metals. In such cases one atom of a univalent metal 
takes the place of one atom of hydrogen, one atom of 
a bivalent metal takes the place of two atoms of hydrogen, 
etc. Thus potassium and sodium are univalent. In the 
formation of potassium nitrate from nitric acid, HNO„ 
one atom of potassium displaces one atom of hydrogen in 



CLASSIFICATION OF TEE ELEMENTS. 129 

the molecule of nitric acid, forming the salt KN0 3 . So 
also sodium nitrate is N~aN0 3 . In the molecule of sul- 
phuric acid, H 2 S0 4 , there are two atoms of hydrogen. To 
displace these, two atoms of a univalent element are re- 
quired. Thus, potassium sulphate is K 2 S0 4 , and sodium 
sulphate is Na 2 S0 4 . Examples of salts containing bivalent 
metals are the following: zinc sulphate, ZnS0 4 , in which 
one atom of bivalent zinc has displaced the two atoms of 
hydrogen of the sulphuric acid ; barium sulphate, BaS0 4 , 
in which one atom of bivalent barium has displaced the two 
atoms of hydrogen of sulphuric acid. When a bivalent 
metal forms a salt with an acid like nitric acid, which con- 
tains but one atom of hydrogen in the molecule, it is be- 
lieved that one atom of the metal acts upon two molecules 
of the acid, thus : 

Pii , HN0 3 _ Pii j NO, , H 



or 



Cu + 2H¥0 3 = Cu(NO,) 9 + H 2 . 



The formula of zinc nitrate is similar, viz., Zn(N0 3 ) 2 . 
In the case of trivalent elements the matter is a little more 
complicated, but still simple enough if it be borne in mind 
that a univalent atom displaces one atom of hydrogen ; a 
bivalent atom displaces two atoms of hydrogen ; a trivalent 
atom displaces three atoms of hydrogen, etc. 

Classification or the Elements. 

Acid Properties and Basic Properties. — The chemical 

properties which force themselves upon our attention most 

prominently in whatever field of chemistry we may be 

working are those which are known as acid properties and 

9 



130 THE ELEMENTS OF CHEMISTRY. 

basic properties. As has already been pointed out, these 
two kinds of properties are the opposite of each other. No 
matter how much chemistry may grow, it is certain that 
the distinction between these two kinds of properties will 
always be recognized as important. 

Acid-forming Elements and Base-forming Elements. — In 
general, both acids and bases contain hydrogen and oxygen, 
There are some elements ivhose compounds ivith hydrogen 
and oxygen have basic properties, and others whose com- 
pounds with hydrogen and oxygen have acid properties 
This important fact may be used as the basis of a partial 
classification of the elements. According to this, we have 
(1) acid-forming elements and (2) base-forming elements. 
Examples of the first class are chlorine, nitrogen, and sul- 
phur. Examples of the second class are sodium, calcium, 
magnesium, etc. The last mentioned are generally called 
metals, and the acid-forming elements are generally called 
non-metals. 

Families of Elements. — Another important fact which is 
soon recognized in studying the elements is that they fall 
into families according to their chemical properties, the 
members of the same family showing striking resemblances 
among one another. Thus, there is the chlorine family, 
which includes, besides chlorine itself, bromine, iodine, 
and fluorine. Further, there is the sulphur family, con- 
sisting of the closely related elements sulphur, selenium, 
and tellurium ; besides other families. In all these cases 
the resemblance between members of the same family is 
striking. 

Families of the Acid- forming Elements. — First, we shall 
have the following families to deal with : 



CLASSIFICATION OF THE ELEMENTS. 131 



Chlorine Family. 


Sulphur Family. 


Nitrogen Family. 


Carbon Family. 


Chlorine, 


Sulphur, 


Nitrogen, 


Carbon, 


Bromine, 


Selenium, 


Phosphorus, 


Silicon. 


Iodine, 


Tellurium. 


Arsenic, 




Fluorine. 




Antimony. 





As the object of your present study is to get a general idea 
of the principles of chemistry, it will not be necessary to 
go into details in dealing with these families. One member 
of each family, except the sulphur family, having been 
treated comparatively fully, the other members may be 
treated briefly. The members of the sulphur family re- 
semble oxygen somewhat, but also differ from it in many 
respects. It will thus be possible to get a clearer idea of 
the principles of chemistry than by attempting to study a 
laro;e number of facts. 



132 THE ELEMENTS OF CHEMISTRY. 






OHAPTEK XV.40KZL 

THE CHLORINE FAMILY: CHLORINE, BROMINE, 
IODINE, FLUORINE. 

Introduction. — The three members of this family which 
show the most marked resemblance are chlorine, bro- 
mine, and iodine. Fluorine is not known in the uncom- 
bined state. Its compounds, however, resemble the com- 
pounds of chlorine, and henco the element is generally 
included in this family. 

Bromine {At. Wt. 80). — This element occurs in nature 
in company with chlorine. Chlorine, as has been stated, 
occurs mostly in combination with sodium, as sodium 
chloride, or common salt. In several of the great salt- 
beds there is some bromine in the form of sodium bromide, 
NaBr, and in some places it occurs as potassium bromide, 
KBr. 

Preparation of Bromine. — The method is the same as 
that made use of for extracting chlorine. In order to get 
chlorine out of common salt, the salt is first converted into 
hydrochloric acid, and this is then oxidized. So, too, in 
order to get bromine out of sodium bromide, the bromide 
must first be converted into hydrobromic acid, and this 
then oxidized. The reactions are 

2NaBr + H 2 S0 4 = Na 2 S0 4 + 2HBr ; 
2HBr + = H 2 + 2Br. 



THE CHLOBINE FAMILY. 133 

Properties of Bromine. — Bromine is a heavy dark-red 
liquid at ordinary temperatures which is easily converted 
into a brownish red vapor. It has an extremely dis- 
agreeable odor. Hence its name from a Greek word mean- 
ing a stench. Its properties are, in general, like those of 
chlorine. It acts violently upon organic substances. It 
attacks the skin and the membranes lining the passages of 
the throat and lungs. Wounds caused by the liquid com- 
ing in contact with the skin are painful and heal with dif- 
ficulty. It must, therefore, be handled with great care. It 
combines with many elements directly and with great 
energy, its compounds with other elements being called 
bromides. While acting in general in the same way as 
chlorine, it is a somewhat weaker element, so that chlorine 
drives it out of its compounds and sets it free. 

Experiment 82. — Mix together about a gram of potassium 
bromide and two grams of manganese dioxide. Pour upon the 
mixture in a good-sized test-tube sufficient dilute sulphuric acid 
to cover it. Heat gently. What do you observe ? Perform this 
experiment where there is a good draught. 

Hydrobromic Acid, HBr. — The only compound which 

bromine forms with hydrogen alone is hydrobromic acid. 

This is in all respects very much like hydrochloric acid. 

Experiment 83. — In a test-tube put a few crystals of potassium 
bromide. Pour on them a few drops of concentrated sulphuric 
acid. The white fumes of hydrobromic acid and the reddish- 
brown vapor of bromine are noticed. Treat a few crystals of 
potassium or sodium chloride in the same way. What difference 
is there between the two cases ? The explanation of the difference 
observed is that sulphuric acid decomposes hydrobromic acid, set- 
ting bromine free, while it does not decompose hydrochloric acid. 

Compounds with Hydrogen and Oxygen. — With hydrogen 

and oxygen bromine forms compounds which resemble very 

closely those which chlorine forms with the same elements. 



134 THE ELEMENTS OF CHEMISTBY. 

The principal ones are bromic, HBr0 3 , and hypolromous 
acids, HBrO, which are like chloric and hypochlorous acids. 

Iodine, I (At. Wt. 127). — This element occurs in nature 
in combination with sodium, in company with chlorine and 
bromine, but in smaller quantity than either. It is also 
found in larger quantity in sea-plants. It is obtained 
largely from the latter source. On the coasts of Scotland 
and France the sea-weed which is thrown up by storms is 
gathered, dried, and burned. The organic portions are thus 
destroyed [what is the meaning of the word destroyed used 
in this sense?], and the mineral or earthy portions are left 
behind as ashes. The incombustible residue is called kelp. 
It contains sodium iodide. At present, in some parts of the 
ocean, sea- weed is cultivated for the sake of the iodine 
which it yields. Chili saltpetre, or the natural sodium 
nitrate found in Chili, contains some sodium iodide, and 
of late this has furnished a considerable quantity of the 
iodine of commerce. 

Preparation of Iodine. — Iodine is prepared from sodium 
iodide, just as chlorine and bromine are prepared from their 
compounds with sodium and potassium. 

Properties of Iodine. — At ordinary temperatures iodine is 
a grayish- black, crystallized solid. It melts easily and boils, 
forming a yiolet-colored vapor. 

Experiment 84. — Mix about 1 gram potassium iodide with 
about twice its weight of manganese dioxide. Treat with a little 
sulphuric acid in a test-tube. Heat gently. Gradually the tube 
will be filled with the beautiful colored vapor of iodine. In the 
upper part of the tube some of the iodine will be deposited in the 
form of crystals of a grayish-black color. 

Iodine dissolves slightly in water, easily in alcohol, and 
easily in a water solution of potassium iodide. 



E 



THE CHLOBmE FAMILY, 135 



Ixperiment 85. — Make solutions of iodine in water, in alcohol, 
and in a water solution of potassium iodide. Use small quantities 
in test-tubes. 

When a solution containing free iodine is treated with a 
little starch-paste the solution turns blue,, in consequence 
of the formation of a complicated compound of starch and 
iodine. Bromine and chlorine do not form blue compounds. 
Advantage is taken of this fact to distinguish between 
iodine and other members of the family. 

Experiment 86. — Make some starch-paste by covering a few 
grains of starch in a porcelain evapo rating-dish with cold water, 
grinding this to a paste, and pouring 200-300 cc. boiling hot 
water on it. After cooling add a little of this paste to a dilute 
water solution of iodine. What change takes place ? Now add 
a little of the paste to a diluted water solution of potassium iodide. 
Is there any change of color ? Acid a drop or two of a solution 
of chlorine in water. What takes place ? Explain what you have 
seen. Does chlorine alone form a blue compound with starch ? 

Hydriodic Acid, HI,, is analogous to hydrochloric and 
hydrobromic acids. It is set free from the iodides by treat- 
ing them with sulphuric acid; but it is even more unstable 
than hydrobromic acid, and hence breaks up into hydrogen 
and iodine. The iodine is set free, while the hydrogen 
acts on the sulphuric acid, as it does in the case of hydro- 
bromic acid. 

Experiment 87 . — Treat a few small crystals of potassium iodide 
with sulphuric acid. [What do you notice ?] Compare with the 
results obtained when potassium bromide and sodium chloride are 
used. 

Fluorine occurs in nature in large quantity, and widely 
distributed, but always in combination with other elements. 
It is found chiefly in combination with calcium, as fluor- 
spar, or calcium fluoride, CaF 2 , and in combination with 
sodium and aluminium, as cryolite, a mineral which oc- 



136 THE ELEMENTS OF CHEMISTRY. 

curs abundantly in Greenland, and has the composition 
3NaF . A1F 3 , being a complex compound of sodium fluoride 
and aluminium fluoride. The element fluorine has not 
been obtained in the free state. 

Hydrofluoric Acid, HP, is made from fluor-spar by treat- 
ing it with sulphuric acid. The action is of the same char- 
acter as that which takes place when hydrochloric acid is 
liberated from sodium chloride: 

CaF 2 + H 2 S0 4 = OaS0 4 + 2HF. 

It is a colorless gas, with strong acid properties. 11 
greatly irritates the membranes lining the throat and lungs 
and hence care should be taken not to inhale it. It acts 
upon glass, dissolving it, and must therefore be kept in 
vessels of rubber, lead, or platinum, upon which it does no 
act. 

Etching on Glass. — The acid is used for etching on glass, 
particularly for marking scales on thermometers, barome- 
ters, and other graduated glass instruments. A solution of 
the gas in water is manufactured for this purpose and kept 
in rubber bottles. 

Experiment 88. — In a lead or platinum vessel put a few grams 
(5-6) of powdered fluor-spar, and pour on it enough concentrated 
sulphuric acid to make a thick paste. Cover the surface of a 
piece of glass with a thin layer of wax or paraffin, and through 
this scratch some letters or figures, so as to leave the glass ex- 
posed where the scratches are made. Put the glass with the 
waxed side downward over the vessel containing the fluor-spar, 
and let it stand for some hours. Then take off the glass, scrape 
off the coating, and the figures which were marked through the 
wax or paraffin will be found etched on the glass. 

Comparison of the Members of the Chlorine Family. — In 
considering, first, the physical properties of these elements, 
you notice that all, with the exception of fluorine, form 






THE CHLORINE FAMILY. 137 

colored gases or vapors. At ordinary temperatures chlorine 
is a gas, bromine a liquid, and iodine a solid. In regard to 
their chemical conduct, it may be said that, in general, 
fluorine is the most active; chlorine comes next in order, 
then bromine, and lastly iodine. 

Their Compounds. — The compounds formed by the three 
elements chlorine, bromine, and iodine with hydrogen and 
oxygen have analogous compositions, and are formed by 
analogous reactions. Thus, there are the hydrogen com- 
pounds: 

HC1, HBr, and HI; 

and the compounds with hydrogen and oxygen: 

HCIO, HBrO. — 
HC10 2 . — — 

HC10 3 , HBr0 3 , HI0 3 . 
HC10 4 , HBr0 4 , HI0 4 . 

Relations between the Atomic Weights. — On comparing 
the atomic weights of chlorine, bromine, and iodine, it 
will be seen that the atomic weight of bromine, which is 
80, is nearly the mean of the atomic weights of chlorine 
and iodine. 

35.5 + 127 = 162.5; 

At. Wt. of At. Wt. of 

chlorine. iodine. 

and — ^— = 81.25, which is nearly the atomic weight of 

bromine. 

Relation between the Properties of the Elements and 
their Atomic Weights. — The properties of the three ele- 
ments chlorine, bromine, and iodine vary with the varia- 



138 THE ELEMENTS OF CHEMISTRY. 

tions in their atomic weights, or with the weights of their 
atoms. The gradation in properties takes place in the 
order chlorine, bromine, iodine, and this is also the order 
in which the atomic weights increase. This may be a 
mere coincidence, but we shall find that in the other fami- 
lies there are similar indications of a close connection be- 
tween the weights of the atoms of the elements and their 
physical and chemical properties. 



THE SULPHUR FAMILY. 133 



CHAPTER XVI. 

THE SULPHUR FAMILY: SULPHUR, SELEKEUM, 
TELLURIUM. 

Sulphur, S {At. Wt. 32). — The principal member of the 
family is sulphur. In nature it is frequently found ac- 
companied by small quantities of selenium, and sometimes 
by tellurium. It has been known in the elementary form 
from the earliest times, for the reason that it occurs abun- 
dantly in this form in nature. It is found particularly in 
the neighborhood of volcanoes, as in Sicily, which is the 
chief source of the sulphur of commerce. It occurs, fur- 
ther, in combination with many metals as sulphides, — as 
in iron pyrites, FeS 2 ; copper pyrites, FeCuS 2 ; galenite, 
PbS, etc. ; in combination with metals and oxygen as sul- 
phates, — for example, as calcmm sulphate, or gypsum, 
CaS0 4 + 2H 2 0; barium sulphate, or heavy spar, BaS0 4 ; 
lead sulphate, PbS0 4 ; and in a few vegetable and animal 
products in combination with carbon, hydrogen, and, gene- 
rally, with nitrogen. 

Extraction of Sulphur from its Ores. — When taken from 
the mines, sulphur is mixed with many earthy substances 
from which it must be separated. This separation is ac- 
complished by piling the ore in such a way as to leave 
passages for air. The piles are covered with some material 
to prevent free access of air, and the mass is then lighted 
below. A part of the sulphur burns, and the heat thus 
furnished melts the rest of the sulphur. The molten sul- 



140 THE ELEMENTS OF CHEMISTRY. 

phur runs doAfn to the bottom of the pile, and is drawn off 
from time to time. 

[If the pile were not protected from free access of air 
what would become of the sulphur? What analogy is 
there between this process and that made use of in making 
charcoal? What are the essential differences between the 
two processes?] 

How Sulphur is Refined. — The crude brimstone first ob- 
tained is afterwards refined by distillation, and it is this 
distilled sulphur which is met with in commerce under the 
names "roll brimstone/' "stick sulphur/' and "flowers of 
sulphur/' The distillation is carried on in earthenware 
retorts connected with large chambers of brick-work. 
When the vapor of sulphur first comes oyer into the con- 
densing chamber it is suddenly cooled, and hence deposited 
in the form of fine powder. This is what is called " flowers 
of sulphur." After the distillation has continued for some 
time the vapor condenses in the form of a liquid, which 
collects at the bottom of the chamber. This is drawn off 
into wooden moulds and takes the form of "roll brim- 
stone" or "stick sulphur." 

Properties of Sulphur. — Sulphur is a yellow, brittle sub- 
stance which at — 50° is almost colorless. It melts at 
111°, forming a thin, straw-colored liquid. When heated 
to a higher temperature it becomes darker and darker in 
color, and at 200° to 250° it is so thick that the vessel con- 
taining it may be turned upside down without danger of 
running out. Finally, at 440° it boils and is then con- 
verted into brownish-yellow vapor. 

Experiment 89. — Distil about 10 grams of roll sulphur from 
an ordinary glass retort. The retort need not be connected with 
a condenser. Notice the changes above described. Collect the 



THE STTLPHTTB FAMILY. 141 

liquid sulphur which passes over in a beaker-glass containing 
cold water. 

Crystals of Sulphur. — When molten sulphur solidifies, or 
when it is deposited from a solution, its particles arrange 
themselves in regular forms called crystals. But, strange 
to say, the crystals formed from molten sulphur are en- 
tirely different from those deposited from solut: .ns of sul- 
phur. Substances which crystallize in two distinct forms 
are called dimorphous. Carbon, like sulphur, crystallizes 
in two different forms [what are they?], and is hence di- 
morphous. 

Experiment 90. — In a covered sand or Hessian crucible melt 
about 20 grams of roll sulphur. Let it cool slowly, and when a 
thin crust has formed on the surface make a hole through this 
and pour out the liquid part of the sulphur. The inside of the 
crucible will be found lined with honey-yellow needles. Take 
out a few crystals and examine them. — Are they brittle or elas- 
tic? What is their color? Are they opaque, transparent, or 
translucent ? — Lay the crucible aside, and in the course of a few 
days again examine the crystals. — What changes, if any, have 
taken place ? 

Solution of Sulphur. — Sulphur is insoluble in water, 
slightly soluble in alcohol and ether. It dissolves in the 
liquid compound of carbon and sulphur known as carbon 
disulphide, CS 2 , and from this solution it is deposited in 
crystals quite different from those obtained in Experiment 
90. 

Experiment 91. — Dissolve 2 to 3 grams roll sulphur in 5 to 10 
cc. carbon disulphide. Put the solution in a shallow vessel, and 
allow the carbon disulphide to evaporate by standing in the 
air. What is the appearance of the crystals? Are they dark 
yellow or bright yellow ? Are they brittle or elastic ? [State in 
tabular form the properties of the two allot ropic forms of sul- 
phur.] 



142 T3E ELBMENTB OF CBEMISTBT. 

Chemical Conduct of Sulphur. — Sulphur combines with 
oxygen when heated to a sufficiently high temperature. 
The product is sulphur dioxide, S0 2 . [Is there any anal- 
ogy between carbon and sulphur in this respect ?] It com- 
bines readily with most metals, forming sulphides. Its 
combination with iron has already been shown in Experi- 
ment 12. It also combines with copper, the act being 
accompanied by light and heat. 

Experiment 92. — In a wide test-tube heat some sulphur to 
boiling. Introduce into it small pieces of copper-foil or sheet- 
copper. Or hold a narrow piece of sheet- copper so that the end 
just dips into the boiling sulphur. What evidence have you that 
action takes place ? 

Hydrogen Sulphide, Sulphuretted Hydrogen, H 2 S. — When 
hydrogen is passed over highly heated sulphur the two ele- 
ments combine to form hydrogen sulphide. [Is there any 
analogy between this process and the formation of water by 
the burning of hydrogen ?] This compound of sulphur 
and hydrogen occurs in nature in solution in the so-called 
"sulphur waters," which are met with in many parts of 
this country as well as in other countries. It also issues 
from the earth in some places. It is formed by heating or- 
ganic substances which contain sulphur, just as water is 
formed by heating organic substances which contain oxy- 
gen, and ammonia by heating such as contain nitrogen. It 
is formed, further, by decomposition of organic substances 
which contain sulphur, as, for example, the albumen of 
eggs. The odor of rotten eggs is partly due to the forma- 
tion of hydrogen sulphide. [How is it that paraffin, p. 107, 
heated with sulphur gives off hydrogen sulphide ?] 

Preparation of Hydrogen Sulphide. — It is made in the 
laboratory by heating a sulphide with an acid. When sul- 



THE SULPHUR FAMILY. 



143 



phuric acid acts upon iron sulphide, hydrogen sulphide is 
given off thus: 

FeS + H 2 S0 4 = FeS0 4 + H 2 S. 

Hydrochloric acid acts in a similar way: 

FeS + 2HC1 = FeCl 2 + H 2 S. 

Experiment 93. — Arrange an apparatus as shown in Fig. 36. 
Put a small handful of sulphide of iron, FeS, in the flask, and 
pour dilute sulphuric acid upon it. Pass the gas through a little 
water contained in the wash-cylinder A. Pass some of the gas 
into water. What evidence have you that it dissolves ? — Collect 
some by displacement of air. It is heavier than air (specific grav- 
ity 1.178). Should the vessel be placed with the mouth down or 
up ? Set fire to some of the gas contained in a cylinder. If there 
is free access of air the sulphur burns to sulphur dioxide, and the 
hydrogen to water. 




Fig. 36. 



Properties of Hydrogen Sulphide. — Hydrogen sulphide, 
or, as it is commonly called, sulphuretted hydrogen, is a 
colorless, transparent gas. It has a disagreeable odor, 
somewhat resembling that of rotten eggs. It is poisonous 



144 THE ELEMENTS OF CHEMISTRY. 

when inhaled in any quantity. It dissolves in water, form- 
ing a solution which has the odor of the gas. Most metals 
when heated in the gas are converted into sulphides. 
Thus, when it is passed over heated iron this reaction takes 
place: 

Fe + H 2 S = FeS + H 2 . 

[What takes place when water vapor is passed over 
heated iron ?] 

Precipitation of Sulphides. — Many of the sulphides are 

insoluble in water. Hence, when hydrogen sulphide is 

passed through solutions containing metals in the form of 

soluble salts, the insoluble sulphides are thrown down, or 

precipitated. 

Experiment 94. — Pass hydrogen sulphide successively through 
solutions containing a little lead nitrate, zinc sulphate, and 
arsenic prepared by dissolving a little white arsenic, or arsenic 
trioxide, As 2 3 , in dilute hydrochloric acid. What do you 
observe in each case? — The substances formed are respectively 
the sulphides of lead, zinc, and arsenic. The reaction in the case 
of zinc sulphate is represented thus: 

ZnS0 4 + H 2 S = ZnS + H 2 S0 4 . 

Chemical Analysis. — In dealing with chemical substances 
the first thing we have to determine is their composition, 
or, in other words, we have to analyze them. For this 
purpose we must first know the properties of the elements 
and their conduct towards chemical substances. To facili- 
tate the process of analysis the mixture to be examined *s 
usually brought into solution and then treated successively 
with certain substances, the effect being observed in each 
case. Suppose we had a solution containing most of the 
metallic elements in the form of salts. If we were to pass 
hydrogen sulphide through this solution, some of the met- 






TEE SULPHUR FAMILY. 145 

als would be precipitated as sulphides, while others would 
remain in solution, as their sulphides are soluble. The 
precipitated sulphides could then be filtered off and exam- 
ined, and the filtered solution also could be further exam- 
ined. Hydrogen sulphide is constantly made use of in the 
laboratory for the purposes of analysis, 

Compounds of Sulphue with Oxygen, and with 
Hydrogen and Oxygen. 

Formation of the Compounds of Sulphur. — When sulphur 
burns in the air, the dioxide, S0 2 , is formed. Under cer- 
tain conditions the dioxide combines with more oxygen, 
forming the trioxide, S0 3 . When sulphur dioxide acts 
upon water, sulphurous acid is formed: 

SO, + H 2 = H 2 S0 3 . 

[Yfhat analogy is there between the acid thus formed 
and carbonic acid?] 

When the trioxide combines with water, sulphuric acid 
is formed: 

S0 8 + H 2 = H 2 S0 4 . 

Sulphur Dioxide, S0 2 . — This compound is formed by 
burning sulphur in the air or in oxygen. It issues from 
volcanoes in large quantities. It is best prepared by heat- 
ing copper with sulphuric acid. We should naturally 
expect the copper simply to take the place of the hydrogen 
of the acid, thus: 

Cu + H 2 S0 4 = CuS0 4 + 2H. 

Probably this action takes place first. But the hydrogen 
10 



146 THE ELEMENTS OF CHEMISTRY. 

acts upon the sulphuric acid, reducing it and forming sul- 
phur dioxide: 

H 2 S0 4 + 2H = 2H,0 + S0 2 . 

[Compare the action of copper on sulphuric acid with 
that of copper on nitric acid. What analogy is there be- 
tween the two cases?] 

Experiment 95. — Put eight or ten pieces of sheet-copper, one 
to two inches long and about half an inch wide, into a 500-cc. 
flask; pour 15 to 20 cc. concentrated sulphuric acid upon it. On 
heating, sulphur dioxide will be evolved. The moment the gas 
begins to come off, lower the flame, and keep it at such a height 
that the evolution is regular and not too active. Pass some of 
the gas into a bottle containing water. Collect a vessel full by 
displacement of air. It is more than twice as heavy as air. See 
whether the gas will burn or support combustion. 

Properties of Sulphur Dioxide. — Sulphur dioxide is a 
colorless gas of an unpleasant, suffocating odor, familiar 
to every one as that of burning sulphur-matches. Water 
dissolves it readily. It bleaches readily, and stops fermen- 
tation. 

Experiment 96. — Burn a little sulphur in a porcelain crucible 
under a bell- jar. Place over the crucible on a tripod some 
flowers. In the atmosphere of sulphur dioxide the flowers will 
be bleached. 

Uses of Sulphur Dioxide. — It is used extensively for the 
purpose of bleaching wool, silk, straw, paper, etc.; and, 
further, to preserve liquids which have a tendency to under- 
go fermentation. If left in the air, fruit-juices become 
sour in consequence of fermentation. As sulphur dioxide 
prevents fermentation, the juices are kept sweet if treated 
with something which gives off the gas, as, for example, a 
sulphite. The principal use of sulphur dioxide is in the 






THE SULPHUR FAMILY. 147 

manufacture of sulphuric acid. For this purpose it is 
made in enormous quantities. 

Sulphurous Acid and Sulphites. — The solution of sulphur 
dioxide in water has acid properties, and contains the acid 
H 2 S0 3 . By neutralizing the solution with bases, the 
sulphites, or salts of sulphurous acid, are obtained. The 
sulphites are analogous to the carbonates in composition, 
and suffer the same decomposition when treated with acids. 
When a carbonate is treated with an acid, carbon dioxide 
is given off. So, also, when a sulphite is treated with an 
acid, sulphur dioxide is given off: 

Na 2 S0 3 + H 2 S0 4 = Na 2 S0 4 + H 2 + SO,; 
Na a SO, + 2H01 = 2NaCl + H 2 + S0 2 . 

Sulphuric Acid, H 2 S0 4 . — Salts of sulphuric acid are found 
in nature, as gypsum, heavy spar, etc. It cannot easily be 
prepared from its salts, as hydrochloric and nitric acids 
are prepared, and is made exclusively by oxidizing sulphur 
dioxide in the presence of water, or, in other words, by 
oxidizing sulphurous acid. The reactions involved in the 
manufacture of sulphuric acid are: 

S + 2 = S0 2 ; 

S0 2 + H 2 = H 2 S0 3 ; 
H 2 S0 3 + = H 2 S0 4 . 

The last reaction cannot readily be effected directly by the 
action of the oxygen of the air, but an extremely interest- 
ing method has been devised by which the oxygen of the 
air is constantly transferred to the sulphurous apd. 

How Nitric Oxide Acts in Oxidizing Sulphurous Acid. — 
The method depends partly upon the power of nitric oxide, 

•1 



148 THE ELEMENTS OF CHEMISTRY. 

NO, to combine directly with the oxygen of the air to 
form nitrogen peroxide, N0 2 . Nitrogen peroxide gives up 
half its oxygen to sulphurous acid, and is itself thus 
reduced to nitric oxide. If, therefore, sulphur dioxide, 
water, and nitrogen peroxide be brought together, the first 
action is represented thus: 

SO, + H 2 + N0 2 = H 2 S0 4 + NO. 

Now, if air be supplied, the nitric oxide will be converted 
into the peroxide: 

NO + = N0 2 . 

The peroxide acting upon a further quantity of sulphur 
dioxide and water is again reduced, and so on indefinitely. 
It will thus be seen that, starting with a small' quantity of 
nitric oxide, it should be possible to convert a large quantity 
of sulphur dioxide into sulphuric acid. 

Manufacture of Sulphuric Acid. — In the manufacture of 
sulphuric acid sulphur or iron pyrites, FeS 2 , is burned. 
In the former case, the only product of the combustion is 
sulphur dioxide; in the latter case, the sulphur forms sul- 
phur dioxide, and the iron is converted into an oxide, 
Fe 2 8 . The sulphur dioxide thus formed is conducted 
into large chambers lined with lead, for the reason that 
sulphuric acid does not act upon lead, while it does act 
upon most other common metals. Instead of starting with 
nitric oxide, nitric acid is passed into the chambers, and 
water in the form of steam. The first action between the 
nitric acid, steam, and sulphur dioxide is this: 

2HN0 3 + 3SO, + 2H 3 = 3H 2 S0 4 + 2N0. 



THE SULPHUR FAMILY. 



149 



From this point sulphur dioxide, water, and nitric oxide 
are brought into action, and the chief reactions are those 
described above. 

A Leaden Chamber. — The arrangement of a leaden 
chamber is shown in Fig. 37. The furnace in which the 
sulphur or iron ppites is burned is represented by /. 
Steam from the boiler b is forced into the chamber through 




Fig. 37. 

jets. The nitric acid is formed from Chili saltpetre and 
sulphuric acid in the furnace n. A good draught is kept 
up by means of a high chimney. 

Ordinary Sulphuric Acid: Oil of Vitriol. — The acid ob- 
tained from the chambers is evaporated in lead pans, and 
afterwards in platinum or glass. The strong acid thus 
obtained is the concentrated sulphuric acid of commerce, 
which is commonly called oil of vitriol. It is an oily liquid, 
usually somewhat colored by impurities. 

The pxire acid is a colorless liquid at ordinary temper- 
atures. When cooled down it forms crystals. It decom- 
poses the salts of most other acids, setting the acids free 
and forming sulphates. You have already had illustrations 
of this power in the liberation of nitric and hydrochloric 
acids from their salts by treatment with sulphuric acid. 

[Give the equations representing the action which takes 



150 THE ELEMENTS OF CHEMISTRY. 

place when common salt and potassium nitrate are treated 
with sulphuric acid.] 

Sulphuric Acid Combines with Water. — Sulphuric acid 
has a very strong tendency to absorb water and form com- 
pounds with it. A great deal of heat is formed in this 
action. This fact has been repeatedly illustrated in ex- 
periments already performed; and attention has been 
called to the necessity for caution in mixing the liquids. 
The acid acts upon organic substances containing hydrogen 
and oxygen, and extracts them in the proportions to form 
water. A piece of wood is charred, if put in the acid, in 
consequence of the abstraction of hydrogen and oxygen. 
[How is wood charred in the preparation of charcoal? Is 
there any analogy between the preparation of charcoal in 
the ordinary way and by the action of sulphuric acid?] 

Wounds caused by sulphuric acid are painful and heal 
with difficulty. 

Importance of Sulphuric Acid. — Sulphuric acid is the 
most important manufactured chemical substance. Most 
chemical industries depend upon it. Among the many 
uses to which it is put are the making of "soda" or 
sodium carbonate, which is necessary for the manufacture 
of soap and glass; the making of phosphorus; of artificial 
fertilizers; the refining of petroleum, etc., etc. In 1883 
there were manufactured 300,000 tons of sulphuric acid in 
the United States, and over 900,000 tons in Great Britain. 

Monobasic and Dibasic Acids. — Sulphuric acid differs 
markedly from nitric and hydrochloric acids in one respect. 
It has the power to form two different salts with the same 
metal, in one of which there is relatively twice as much of 
the metallic element as in the other. If to a given quan- 
tity of sulphuric acid there be added only half the quantity 



THE SULPHUR FAMILY. 151 

of caustic potash required to neutralize it, a salt is formed 
which crystallizes. It has the composition represented by 
the formula KHS0 4 . If nitric acid be treated in the same' 
way, only half the acid is acted on, and this forms ordi- 
nary potassium nitrate, KN0 3 , the rest of the acid being 
left unacted upon. In the case of sulphuric acid two 
reactions are possible, viz. : 

H 2 S0 4 + KOH = KHS0 4 + H 2 0; 

H 2 S0 4 + 2KOH ±= K 2 S0 4 + 2H 2 0. 

In the case of nitric acid only one reaction seems to be 
possible : 

HN0 3 + KOH = KN0 3 + H0 3 . 

Acids which, like sulphuric acid, have the power to form 
two salts with the same metal are called dibasic acids. 
Acids which, like nitric acid, have the power to form only 
one salt with the same metal are called monobasic acids. 
This power is connected with the number of replaceable 
hydrogen atoms contained in the molecule of the acid. 
An acid containing two replaceable hydrogen atoms in its 
molecule is dibasic ; one containing only one replaceable 
hydrogen atom in its molecule is monobasic. 

Acid, Neutral, and Normal Salts. — A dibasic acid yields 
two classes of salts : (1) those in which all the hydrogen is 
replaced, and (2) those in which half the hydrogen is re- 
placed by metal. The former are called normal salts, the 
latter acid salts. Normal salts are generally neutral, and 
are sometimes called neutral salts. 

Carbon Bisulphide, CS 2 . — Sulphur forms with carbon a 
compound called carbon disulphide, which has the compo- 



152 THE ELEMENTS OF CHEMISTRY. 

tion 0S 2 . It is made by bringing carbon and sulphur to- 
gether at high temperatures. It is a liquid which boils at 
47°. That it dissolves sulphur has been shown in Experi- 
ments 11 and 91. It also dissolves many other substances. 

Selenium, Tellurium, and their Compounds. — These ele j 
ments are rarely met with. In general their properties are 
very similar to those of sulphur, and they form compounds 
analogous to the principal compounds of sulphur. 

Relations between the Atomic Weights of Sulphur, Sele- 
nium, and Tellurium. — The relation between the atomic 
weights of the members of the sulphur family is like that 
already noticed between the atomic weights of the members 
of the chlorine family. It is shown thus : 

32 + 125.2 =157; 

At. Wt. of At. Wt. of 

sulphur. tellurium. 

157 2 
and — ^— = 78.6, which is nearly 79, the atomic weight of 

selenium. 



THE NITROGEN FAMILY. 153 



CHAPTER XVII. 

THE NITROGEN FAMILY: NITROGEN, PHOSPHORUS, 
ARSENIC, AND ANTIMONY. 

Boikxn" and Silicon. 

Phosphorus, P (At. Wt. 31). — Phosphorus occurs in the 
form of phosphates, or salts of phosphoric acid. The chief 
of these is calcium phosphate, which is the principal con- 
stituent of the minerals phosphorite and apatite, and of the 
ashes of bones. 

Phosphorus Made from Bones. — It is made from bone-ash, 
which contains a large proportion of calcium phosphate. 
The ash is first mixed with sulphuric acid. Then the 
compound thus obtained is mixed with charcoal and 
heated, when phosphorus distils over. It is cast into 
sticks under water, and kept under water. 

Properties. — It is colorless or slightly yellow and trans- 
lucent. At ordinary temperatures it can be cut like wax, 
but it becomes hard and brittle at lower temperatures. It 
melts at 44°, and boils at 290°. Unless carefully protected 
from the light its appearance changes. It becomes opaque 
and dark in color, and finally dark red. This change can 
be hastened by heating the phosphorus in a sealed tube to 
250°. Ordinary phosphorus is insoluble in water, but solu- 
ble in carbon disulphide. In contact with the air it gives 
off fumes which emit a pale light visible in a dark room. 
It takes fire when rubbed or cut, and must hence b§ 



154 THE ELEMENTS OF CHEMISTRY. 

handled with great care. It should always be cut under 
water, and never held in the hand. It not only combines 
with oxygen easily, but with other elements, such as chlo- 
rine, bromine, and iodine. 

Experiment 97. — Bring together in a porcelain crucible or 
evaporating-dish a little phosphorus and iodine. It will be seen 
that simple contact is sufficient to cause the two substances to 
act upon each other. Direct combination takes place, and the 
action is accompanied by light and heat. 

Phosphorus is very poisonous. Its vapor produces a 
disease of the bones. 

Red Phosphorus. — The red substance formed when ordi- 
nary phosphorus is left in the light, or heated without ac- 
cess of air, is a second variety of phosphorus, known as red 
phosphorus. This differs from ordinary phosphorus as 
much as graphite differs from the diamond. Ordinary 
phosphorus is very active, combining readily with oxygen; 
it is soluble in carbon disulphide; and is poisonous. Eed 
phosphorus, on the other hand, is inactive. It does not 
change in the air, and requires to be heated to a compara- 
tively high temperature before it will combine with oxygen; 
it is insoluble in carbon disulphide, and is not poisonous. 
It is converted into the ordinary variety when heated to 
about 300°. [Make out a tabular comparison of the pro- 
perties of the two allotropic forms of phosphorus.] 

Uses of Phosphorus. — The principal use of phosphorus is 
in the manufacture of matches. Ordinary friction-matches 
are tipped with a mixture of phosphorus, glue, and potas- 
sium chlorate. " Safety-matches" are usually tipped with 
potassium chlorate and antimony sulphide. The surface 
upon which they are rubbed is made of red phosphorus, 
black oxide of manganese, and glue. Mixed with flour, 
phosphorus is frequently used as a rat-poison ? 



TEE NITBOGEN FAMILY. 155 

Compounds of Phosphorus with Oxygen and with Hydro- 
gen and Oxygen. — When phosphorus is burned in the air 
or in oxygen it is converted into the oxide, P 2 5 . This 
combines with water in different proportions, forming two 
distinct acids, known as metaphosphoric and orthophospho- 
ric acids : 

P.O.+ H 2 0= 2HPO,; 

Metaphosphoric acid. 

P,0 6 + 3H s O=2H a P0 4 . 

Orthophosphoric acid. 

Orthophosphoric or Ordinary Phosphoric Acid, H 3 P0 4 , is 

the principal compound of phosphorus. It is the final 
product of the action of air and moisture on phosphorus. 
As has been stated, it occurs in nature as the calcium salt 
in phosphorite and apatite. This salt is also the chief 
constituent of bone-ash. It is a solid crystallized sub- 
stance, and is made by treating bone-ash with sulphuric 
acid, or by oxidizing phosphorus. It has the power of 
forming three distinct salts with the same metal, and is 
hence called tribasic. With sodium, for example, it forms 
the three salts Na 3 P0 4 , Na a HP0 4 , and NaH 2 P0 4 . Its 
normal calcium salt — that is to say, the one in which all 
the three acid hydrogen atoms are replaced by calcium — ■ 
has the formula Ca 3 (P0 4 ) 2 , three bivalent calcium atoms 
replacing six atoms of hydrogen. 

Arsenic and its Compounds. — Arsenic, As (At. Wt. 75), 
occurs in nature in combination with metals, — as, for ex- 
ample, iron, copper, cobalt, nickel, etc., — and in combina- 
tion with oxygen as the oxide As 2 3 . It has a metallic 
lustre. When heated to quite a high temperature in the 
air it takes fire, and burns with a bluish flame, giving off 
a smoke which has the odor of garlic and is poisonous. It 



156 



THE ELEMENTS OF CHEMISTBY. 



combines directly with most elements. In the elementary 

form it is not poisonous, but when oxidized it becomes so. 

Arsine, Arseniuretted Hydrogen, AsH 3 . — This compound, 

which in composition is analogous to ammonia, NH 3 , is 

made by bringing a compound of arsenic with oxygen into 

a mixture from which hydrogen is being evolved. 

Experiment 98. — Arrange an apparatus as shown in Fig. 38. 
Put some granulated zinc in the flask and pour dilute sulphuric 




Fig. 38. 



acid on it. When the air is all out of the vessel and the hydro- 
gen is lighted, add slowly a little of a solution of arsenic oxide, 
As 2 3 , in dilute hydrochloric acid. What change takes place in 
the flame ? Is the color changed ? Are fumes given off ? (See 
Experiment 99.) 

Arsine is a colorless gas which is very poisonous and has 
an unpleasant odor. When lighted it burns with a bluish- 
white flame. It is very unstable, breaking up into arsenic 
and hydrogen when heated. When a cold object, as a 
piece of porcelain, is brought into the flame of burning 
arsine, the arsenic is deposited in the form of a dark spot. 



THE NITROGEN FAMILY. 157 

Detection of Arsenic in Cases of Poisoning. — The con- 
duct of arsine is taken advantage of for the purpose of de- 
tecting the presence of arsenic. It is extensively used in 
examining the stomach and other viscera of human beings 
in cases of suspected poisoning. The method used is 
known as Marsh's test, having been introduced by a chem- 
ist by the name of Marsh. 

Experiment 99. — Into the flame of the burning hydrogen and 
arsine produced in the last experiment introduce a piece of por- 
celain, as the bottom of a small porcelain dish or a crucible, or a 
bit of a broken plate, and notice the appearance of the spots. 
Heat by means of a Bunsen burner the tube through which the 
gas is passing, which should be of hard glass. Just in front of 
the heated place there will be deposited a thin layer of metallic 
arsenic, commonly called a mirror of arsenic. This deposit is due 
to the decomposition of the arsine into arsenic and hydrogen by 
heat. 

Arsenic Tri oxide, As 2 3 . — When arsenic is burned in the 
air or oxygen it forms the trioxide. [Compare with phos- 
phorus in this respect.] This substance, which is what is 
commonly called arsenic, or tvhite arsenic, is made by heat- 
ing compounds of arsenic and metals in contact with the 
air. Under these circumstances both the metal and the 
arsenic are oxidized, and the oxide of arsenic, being vola- 
tile, passes off and is condensed and collected in large 
chambers of mason-work. It is a colorless, glassy mass. 
It is difficultly soluble in water, more easily in hydrochloric 
acid. It has a weak, disagreeably sweet taste, and acts 
very poisonously. It is probably more frequently used as a 
poison than any other substance. Minute quantities can 
be detected by the chemist with absolute certainty. It is 
easily reduced by means of carbon. 

Experiment 100. — Mix together about equal small quantities 
of arsenic oxide and finely-powdered charcoal. Heat the mixture 



158 THE ELEMENTS OF CHEMISTRY. 

in a small dry tube of hard glass, closed at one end. The arsenic 
which is set free will be deposited on the walls of the tube in the 
form of a mirror, like that obtained in Experiment 100. 

Antimony, Sb (At. Wt. 120), occurs most frequently in 
combination with sulphur as the sulphide Sb 2 S 3 . It is a 
silver- white, metallic-looking substance. At ordinary tem- 
peratures it is not changed by contact with the air; but 
when heated to a sufficiently high temperature it takes fire 
and burns, forming the white oxide. 

Stibine, Antimoniuretted Hydrogen, SbH 3 . — This com- 
pound is made by the same method as that described under 
Arsenic. 

Experiment 101. — Make some stibine, using a solution of tar- 
tar emetic, a substance which contains antimony. 

Its properties are very much like those of arsine. It 
burns with a similar flame, and is decomposed in the same 
way. 

Experiment 102. — Introduce a piece of porcelain in the flame 
and notice the deposit or antimony spot. It is darker and more 
smoky than the arsenic spot. There are other differences in prop- 
erties, but they need not be considered here. 

Boron, B (At. Wt. 10.9). — Boron may conveniently be 
considered in connection with the nitrogen family, as some 
of its properties suggest those of the members of that 
family. At the same time, it has peculiarities which dis- 
tinguish it from these elements. It occurs in nature in 
the form of ioric acid, or as salts of this acid, particularly 
the sodium salt, or lorax. It is prepared by treating the 
oxide, B 2 3 , at a very high temperature with sodium or 
aluminium. Under proper conditions it is obtained in 
the form of crystals, which are almost as hard as diamonds. 

Tetraboric Acid, H 2 B 4 7 , is the form of boric acid from 



THE G ABB ON FAMILY. 159 

which borax is derived. The formula of borax is Na 2 B 4 7 
+ 10H 2 O, 

The Carbon Family: Carbon a^d Silicon. 

Occurrence of Silicon. — Carbon, as you have seen, occurs 
in every living thing. It is interesting to note that silicon, 
which in some respects resembles carbon in its chemical 
properties, is one of the most important constituents of the 
mineral or inorganic parts of the earth. It occurs chiefly 
in the form of the oxide, Si0 2 , commonly called silica, or 
silicon dioxide; and in combination with oxygen and 
several of the common metals, particularly with sodium, 
potassium, aluminium, and calcium, in the form of the 
silicates. 

Great Abundance of Silicon. — Next to oxygen silicon 
occurs in largest quantity in the earth. There are exten- 
sive mountain-ranges consisting almost entirely of silicon 
dioxide, Si0 2 , in the form known as quartz or quartzite. 
Other ranges are made up of silicates, which are compounds 
formed by a combination of silicon dioxide and bases. 
The clay of valleys, river-beds, etc., also contains silicon 
in large quantity, while the sand found so abundantly at 
the seashore is mostly silicon dioxide, Si0 2 . 

The Element Silicon. — Unlike carbon, silicon is never 
found in the uncombined state. It is an extremely difficult 
thing to decompose the oxide in such a way as to get the 
element. Under proper conditions silicon can be obtained 
in the form of crystals which have a gray color and are 
harder than glass. 

Silicic Acid. — There are several varieties of silicic acid, 
all of which are, however, derived from an acid of the 



160 THE ELEMENTS OF CHEMISTRY. 

formula ET Si(X, or normal silicic acid. When this is set 
free from its salts it loses water, and is changed to ordinary 
silicic acid, H 2 Si0 3 : 

H 4 SiO< = H 2 Si0 3 + H 2 0. 

When heated higher, this second form of silicic acid is con- 
verted into the dioxide Si0 2 : 

H 2 Si0 3 = Si0 2 + H 2 0. 

Silicon Dioxide, Silicic Anhydride, Si0 2 . — As already 
stated, this substance occurs very abundantly in nature and 
in many different forms. Quartz, or rock crystal, is pure 
crystallized silicon dioxide; quart zite is a coarser-grained 
substance made up of small crystals of quartz, usually col- 
ored. Agate, amethyst, and carnelian are varieties of quartz 
colored by foreign substances. Silica also occurs in the 
stalks of some plants, giving them firmness, and in some 
cases making them so hard that they are valuable for pol- 
ishing. 

Some of the more important silicates, as water-glass, glass, 
and the natural silicates, will be considered farther on. 



BASE-FOBMING ELEMENTS. 161 



OHAPTEE XVIII. 

BASE-FORMING ELEMENTS— GENERAL CONSIDERA- 
TIONS. 

Distinction between Acid-forming and Base-forming Ele- 
ments. — The meaning of the name base-forming elements 
is simply that the compounds of these elements with hy- 
drogen and oxygen are bases, or, in other words, have the 
power to neutralize acids and form salts. But the distinc- 
tion between acid-forming and base-forming elements is 
not a sharp one, for the reason that there are some elements 
which form both acids and bases. 

Base-forming Elements. — The base-forming elements will 
be taken up in the following order: 

1. The Potassium Family, the principal members of 
which are potassium and sodium. 

2. The Calcium Family, the principal members of 
which are calcium, barium, and strontium. 

3. The Magnesium Family, the principal members of 
which are magnesium and zinc. 

4. The Silver Family, consisting of silver, copper, and 
mercury. 

5. The Aluminium Family, of which aluminium is the 
only well-known member. 

6. The Iron Family, consisting of iron, cobalt, and 
nickel. 

7. The Manganese Family, of which manganese is the 

only representative. There are some points of resem- 
11 



162 THE ELEMENTS OF CHEMISTRY. 

blance between manganese and the members of the 
chlorine family. 

8. The Chromiu?n Family, of which chromium is the 
principal member. There are some points of resemblance 
between chromium and the members of the sulphur family. 

9. The Bismuth Family, of which bismuth is the only 
representative. Between it and the members of the nitro- 
gen family there are some points of resemblance. 

10. The Lead Family, the principal members of which 
are lead and tin. 

11. The Palladium Family, consisting of three rare 
elements. 

12. The Platinum Family, the principal members of 
which are platinum and gold. 

Large Number of Base-forming Elements. — You see that 
there are many more base-forming than acid-forming 
elements, and it is a serious undertaking to become 
thoroughly acquainted with all the elements included 
under this head. For the present it will be best to confine 
our attention to a few of the most important of the ele- 
ments. 

Metallic Properties. — The base -forming elements are 
those which are usually called metals. The name metal 
is applied to those elements which have what is known as 
a metallic lustre, are opaque, and are good conductors of 
electricity. Gradually the name metal has come- to mean an 
element which has the power to displace the hydrogen of 
acids and form salts. 

Classes of Metal Derivatives. — As the metals or 
forming elements all combine with oxygen, sulphur, 
chlorine, and also form salts with all acids, it follows that 
under the head of each one there must be a large number 



BASE-FORMING ELEMENTS. 1 63 

of compounds. A thorough study of each metal would 
include the following subjects: 

1. Its Occurrence in Nature. — Under this head we 
should become acquainted with those natural compounds 
of the metals known as minerals. Those minerals from 
which the metals are extracted for practical purposes are 
called ores. 

2. Extraction of the Metals from their Ores. — The study 
of this subject is the object of metallurgy. 

3. The Properties of Metals. — As you will find, metals 
differ very markedly from one another. Some are light, 
floating on water, as potassium, sodium, etc. ; some are ex- 
tremely heavy, as lead, platinum, etc. Some combine 
with oxygen with great energy; others form very weak 
compounds with oxygen. Some form strong bases; others 
form weak bases. 

4. The Compounds of the Metals. — These may be con- 
veniently classified as: 

a. Compounds with chlorine, bromine, and iodine; or 
the chlorides, bromides, and iodides. 

b. Compounds with oxygen and with oxygen and hydro- 
gen; or the oxides and hydroxides. 

c. Compounds with sulphur and with sulphur and hy- 
drogen; or the sulphides and hydrosulphides. 

d. Compounds with nitric and nitrous acids; or the 
nitrates and nitrites. 

e. Compounds with the acids of chlorine; or the chlo- 
rates, chlorites, etc. 

/. Compounds with sulphuric and sulphurous acids; or 
the sulphates and sulphites. 

g. Compounds with carbonic acid; or the carbonates. 
h. Compounds with phosphoric acid; or the phosphates. 



164 



THE ELEMENTS OF CHEMISTBY. 



i. Compounds with silicic acid; or the silicates. 

j. Compounds with boric acid; or the borates. 

The acids of which the salts are derivatives are already 
known to you, and in dealing with the acids frequent 
reference has been made to the methods of making the 
salts, and to some of their most important properties. In 
what follows only those compounds will be considered 
which well illustrate general principles, or which, owing 
to some familiar application, happen to be of special 
interest. 



THE POTASSIUM FAMILY. 165 



CHAPTEE XIX. 

THE POTASSIUM FAMILY: POTASSIUM, SODIUM 
(AMMONIUM). 

Alkalies. — The members of this family are generally 
called metals of the alkalies, as the two best-known mem- 
bers are obtained from the alkalies, caustic potash and 
caustic soda, or potassium and sodium hydroxides. 

Potassium, K (At. Wt. 39). — This element is a constitu- 
ent of many minerals, particularly of feldspar, which is a 
silicate of aluminium and potassium. 

In the Soil.— The natural decomposition of minerals con- 
taining potassium gives rise to the presence of this element 
in various forms of combination everywhere in the soil, and 
it is of the highest importance for the plants, as they use it 
as part of their food. When vegetable material is burned 
the potassium remains behind, chiefly as potassium carbon- 
ate. When wood-ashes is treated with water the potas- 
sium carbonate dissolves, and it is obtained in an impure 
state by evaporating the solution. The substance thus ob- 
tained is called potash. 

Experiment 103. — Treat two or three pounds of wood-ashes 
with water. Filter off the solution, and examine it by means of 
red litmus-paper. Is the solution alkaline ? Examine some po- 
tassium carbonate. — Does its solution act in the same way ? — 
Evaporate to dryness the solution obtained from the wood-ashes. 
Collect the dry residue and treat it in a test-tube with a little 
dilute hydrochloric acid. Is a gas given off ? Is it carbon diox- 
ide ? 



166 THE ELEMENTS OF CHEMISTRY. 

Potassium is also found in the form of the chloride KOI, 
accompanying the chloride of sodium, and as the nitrate in 
saltpetre. 

How Potassium is Prepared. — The metal was first pre- 
pared by the action of a powerful electric current on caustic 
potash, which had been considered as an element. It is 
now manufactured by distilling a mixture of potassium 
carbonate and charcoal: 

K 2 C0 3 + 20 = 2K + 300. 

Properties. — It is a light substance which floats on 
water. Its freshly-cut surface has a bright metallic lustre, 
almost white ; it acts upon water with great energy, caus- 
ing the evolution of hydrogen, which burns, and the for- 
mation of potassium hydroxide. In consequence of its 
action on water, potassium cannot be kept in the air. It 
is kept under some oil upon which it does not act, as pe- 
troleum. 

Experiment 104. — Throw a small piece of potassium not larger 
than the size of a pea upon water. What takes place ? What is 
the color of the flame ? What difference is there between the 
action of sodium and of potassium on water ? Is the solution 
after the action alkaline ? Why ? 

Compounds of Potassium. — The chief compounds of po- 
tassium with which we meet are the iodide, KI; the hydrox- 
ide, or caustic potash, KOH; the nitrate, or saltpetre, 
KN0 3 ; the chlorate, KC10 3 ; and the carbonate, K 2 C0 3 . 

Potassium Iodide, KI, is made by treating caustic potash 
with iodine. The action is the same as that which takes 
place when chlorine acts upon warm concentrated caustic 
potash. Both the iodide and iodate are formed: 

6K0H + 61 - 5KI + KI0 3 + 3H A 



THE POTASSIUM FAMILY. 167 

By evaporating off the water and heating the residue, 

the iodate is decomposed into iodide and oxygen. 

Experiment 105. — Examine a bottle of crystallized potassium 
iodide. Taste a little. Dissolve some in water. Add some 
iodine to this solution. Does the iodine dissolve ? Heat a little. 
Does the substance contain water of crystallization ? Treat a 
crystal or two with a few drops of concentrated sulphuric acid. 
What takes place ? To what is the appearance of violet vapors 
due ? See Experiment 87. 

Potassium iodide is extensively used in medicine and in 
photography. 

Potassium Hydroxide, KOH. — This well-known sub- 
stance, commonly called caustic potash, is prepared by heat- 
ing potassium carbonate with lime (calcium hydroxide) in 
a silver or iron vessel. 

Experiment 106. —Dissolve 50 grams potassium carbonate in 
500-600 cc. water. Heat to boiling in an iron or silver vessel, 
and gradually add slaked lime made from 25 to 30 grams good 
quicklime. During the operation the mass should be stirred 
with an iron spatula. After the solution is cool, draw it off by 
means of a glass siphon into a bottle. This may be used in ex- 
periments in which caustic potash is required. The reaction is 
based upon the fact that calcium carbonate is insoluble, and that 
potassium carbonate and calcium hydroxide are soluble: 

K 2 C0 3 + Ca0 2 H 2 = CaCOs + 2KOH. 

The hydroxide is a white brittle substance. In contact 
with the air it deliquesces [what does this mean-?] and ab- 
sorbs carbon dioxide. It is a strong base. [What prod- 
ucts are formed when it acts upon hydrochloric acid ? 
Upon nitric acid ,? Upon sulphuric acid? How many 
salts can it form with sulphuric acid ? What are their 
formulas ?] 

Potassium Nitrate, KN0 3 — The common name of this 
salt is saltpetre. Its occurrence in nature has already been 



168 THE ELEMENTS OF CHEMISTRY. 

referred to. When refuse animal matter is left to un- 
dergo decomposition in the presence of bases, nitrates are 
formed. 

Saltpetre Plantations. — Advantage is taken of the fact 
just mentioned for the purpose of preparing saltpetre arti- 
ficially. Heaps of refuse matter from stables are mixed 
with lime and kept moist, and then allowed to stand for a 
time. The nitrate which is formed is extracted with water, 
converted into potassium nitrate, and purified. Places 
where this process is carried on on the large scale are 
called saltpetre plantations. 

Properties.— Potassium nitrate crystallizes in long rhom- 
bic prisms which have a salty taste. It is easily soluble in 
water. 

Uses of Saltpetre. — It is used in making sulphuric acid 
[how?], and nitric acid [how?]. Its chief use is in the 
manufacture of gunpowder. 

Gunpowder. — The value of gunpowder is due to the fact 
that it explodes readily, the explosion being a chemical 
change accompanied by a sudden evolution of gases. When 
the powder is enclosed in a gun-barrel the gases in escaping 
drive the ball before them. Gunpowder has long been 
known, and has always been made of saltpetre, charcoal, and 
sulphur. When heated the saltpetre gives off oxygen and 
nitrogen; the oxygen combines with the charcoal, forming 
carbon dioxide, and the sulphur combines with the potas- 
sium, forming potassium sulphide. The reactions are 
represented in this equation: 

2KN0 3 + 30 + S = 3C0 2 + 2N + K 2 S. 

Gas. Gas. Solid. 

Experiment 107. — Mix together 15 grams potassium nitrate 
and 2.5 grams powdered charcoal. Set fire to the mass. 



THE POTASSIUM FAMILY. 169 

Potassium Chlorate, KC10 3 , has so frequently been re- 
ferred to and used in earlier experiments that it is not 
necessary to say anything more about it now. 

[Describe the method of preparation and decomposition 
by heat.] 

Sodium, Na {At. Wt. 23). — Sodium occurs very widely 
distributed and in large quantities, principally as sodium 
chloride. It occurs also as sodium nitrate, and as silicate 
in many minerals. Like potassium it is found everywhere 
in the soil, and is taken up by plants, especially by those 
which grow in the neighborhood of the sea and in the sea. 

Preparation of Sodium. — Sodium is made by the same 
method as that used for making potassium. 

Properties, — Its properties are very similar to those of 
potassium. It is light, floating on water; it has a bright 
metallic lustre, and is soft, like wax. It decomposes water, 
but not as actively as potassium. 

Sodium a Strong Reducing Agent. — Sodium has a strong 
attraction for oxygen, and is used in some chemical pro- 
cesses as a reducing agent, as, for example, in the prepara- 
tion of aluminium. A compound of mercury and sodium, 
known as sodium amalgam, is used in some metallurgical 
operations connected with the extraction of gold and silver 
from their ores. 

Compounds of Sodium. — The chief compounds of sodium 
are the chloride, KTaCl; the hydroxide, or caustic soda, 
NaOH; the nitrate, or Chili saltpetre, NaN0 3 ; the sul- 
phate, JSTa 2 S0 4 ; the carlonate, Na 2 C0 3 ; and the lor ate, or 
borax, Na 2 B 4 7 . 

Sodium Chloride, NaCl. — This is the substance known by 
the name common salt. It occurs very widely distributed, 
and, as it is easily soluble, much of the water which enters 



170 THE ELEMENTS OF CHEMISTRY. 

into the ocean contains some of it in solution. Sea-water 
contains 2% to 3 per cent of sodium chloride. 

How Salt is Obtained. — In some places salt is taken out 
of mines in the solid form; in others water is allowed to 
flow into the mines, and to remain* for some time in contact 
with the salt, and the solution thus formed is drawn or 
pumped out of the mine and evaporated by appropriate 
methods. Salt is also obtained from the sea in hot coun- 
tries. At high tide the water is dammed up, and the arti- 
ficial ponds thus formed afterwards evaporate under the 
influence of the sun, leaving the salt behind. 

Properties. — Sodium chloride crystallizes in colorless and 
transparent cubes. Sometimes that which occurs in nature 
is colored blue. Its taste is familiar to every one. 

Uses of Salt. — Salt is an extremely important article of 
food. It appears to be necessary to the life of man as well 
as of many animals. It is found in all parts of the body. 
It is used to prevent decomposition of meats. Salt pork 
and salt fish are familiar to all. Salt is used as the starting- 
point in the preparation of all sodium compounds and of all 
chlorine compounds. 

[How are chlorine and hydrochloric acid obtained from 
it?] 

Sodium Hydroxide, NaOH. — This is commonly called 
caustic soda. It can be prepared in the same way as potas- 
sium hydroxide; that is, by treating a solution of sodium 
carbonate with lime. [Explain the reaction.] Its prop- 
erties are very similar to those of caustic potash. 

Sodium Nitrate, "N"aN"O s . — This is the salt which has 
been repeatedly referred to by the name of Chili saltpetre. 
It occurs in very large quantities, and is the chief source of 
nitric acid. It is cheaper than potassium nitrate, but can- 



THE POTASSIUM FAMILY. Ill 

not be substituted for it in the manufacture of gunpowder, 
because it becomes moist in the air. It is converted into 
potassium nitrate by treating its solution with potassium 
chloride: 

MaNO, + KOI = KN0 3 + NaOl. 

Sodium Sulphate, Na 2 S0 4 + 10H 2 O. — The common 
name of this substance is Glauber's salt. It is manufac- 
tured in enormous quantities for the purpose of converting 
common salt into sodium carbonate or "soda:" 

2NaCl + H 2 S0 4 = 2HC1 + Na 2 S0 4 . 

It crystallizes in large, colorless, monoclinic prisms, 
containing 10 molecules of water of crystallization, 
Na 2 S0 4 + 10H 2 O. It loses water when left in contact with 
the air. 

Sodium Carbonate, Na 2 C0 3 + 10H 2 O. — This salt, com- 
monly called soda, is one of the most important of manu- 
factured chemical substances. The mere mention of the 
fact that it is essential to the manufacture of glass and soap 
will give an idea of its importance. It is found in the ashes 
of sea-plants, just as potassium carbonate is found in the 
ashes of land-plants. Formerly it was obtained from this 
source. Now, however, we are not dependent upon sea- 
plants for our supply, as two methods have been devised 
for preparing it from sodium chloride, with which the earth 
is so abundantly supplied. 

Manufacture of Soda from Sodium Chloride. — During 
the French Eevolution the supply of soda was cut off from 
France, and the government therefore offered a large prize 
for a method for making it from common salt. A method 
was devised by Leblanc which has been used very exten- 
sively ever since. 



172 THE ELEMENTS OF CHEMISTRY. 

Leblanc's Method for Making Soda. — This consists of four 
reactions : 

1st. The sodium chloride is converted into sodium sul- 
phate by treating it with sulphuric acid : 

2NaCl + H 2 S0 4 = Na 2 S0 4 + 2HC1. 

2d. The sodium sulphate thus obtained is heated with 
charcoal, which reduces it to sodium sulphide, ]STa 2 S: 

Na 2 S0 4 + 40 = Na 2 S + 4C0. 

3d. The sodium sulphide is heated with calcium carbon- 
ate, when sodium carbonate and calcium sulphide are 
formed : 

Na 2 S + CaC0 3 = Na 2 C0 3 + OaS. 

4th. If lime is present in the last reaction, it forms an 
insoluble compound with calcium sulphide. By treating 
the product of the reaction with water the sodium carbon- 
ate alone dissolves. 

In practice the sodium sulphate is mixed with charcoal 
and calcium carbonate and the mixture heated. 

The Solvay Method. — Another method has recently come 
into great prominence, threatening to drive out the Le- 
blanc method completely. This is the Solvay, or the am- 
monia, method. This depends upon the fact that the salt, 
HNaCOg, is comparatively difficultly soluble in water and 
is therefore precipitated from a solution of common salt by 
the addition of an easily soluble carbonate.* 

* In 1883 there were manufactured in Germany 115,500 tons of 
carbonate of soda, half of it by the Solvay method. In the same year 
429,040 tons were manufactured in England by the Leblanc process* 



TSE POTASSIUM FAMILY. 175 

Properties.— Sodium carbonate crystallizes in large prisms 
with 10 molecules of water of crystallization. The crystals 
are efflorescent. 

Mono-sodium Carbonate, HNaC0 3 , or Mcarlonate of soda, 
is made from sodium carbonate by passing carbon dioxide 
into it: 

Na 2 C0 3 + C0 2 + H 2 = 2HNaC0 8 . 

This substance is one of the constituents of laking-pow- 
ders which are used for raising bread. Roclielle powders con- 
sist of the bicarbonate and cream of tartar mixed together. 
When water is added to the mixture, carbon dioxide is 
given off, as the cream of tartar is an acid salt, acid potas- 
sium tartrate, KH 5 C 4 6 , and Roclielle salt is left in solu- 
tion. This is the potassium and sodium salt of tartaric 
acid, of the composition ENaH 4 C 4 6 . [Why are such 
salts called double salts?] 

Disodium Phosphate, Na 2 HP0 4 + 12H 2 0.— This is the 
common form of sodium phosphate. 

Sodium Borate, Borax, ¥a 2 B 4 7 + 10H 2 O. — This salt is 
found in several lakes in Asia, and in this country in Clear 
Lake, Nevada. It is also manufactured by neutralizing the 
boric acid found in Tuscany. When heated, borax puffs 
up, and at red heat melts, forming a transparent, colorless 
liquid. This is the dry substance, Na 2 B 4 7 . Molten borax 
has the power to dissolve the oxides of the metals, and 
forms colored glasses with some of them. In soldering 
it is necessary that the metals should be clean and bright. 
To secure this a little molten borax is put on the surfaces 
which are to be united. Borax is an antiseptic; that is to 
say, it prevents the decomposition of organic subtances. 



174 THE ELEMENTS OF CHEMISTRY. 

Water-glass. — Silicon dioxide, or silica, Si0 2 , dissolves 
by continued boiling with caustic soda or potash, and so- 
dium or potassium silicate is thus formed: 



Si0 2 + 2NaOH = Na 2 Si0 3 + H 2 0. 






These salts are soluble in water, and are known as water- 
glass. Water-glass is used in making artificial stone, and 
for the purpose of protecting certain stones from the action 
of the weather. 

Ammonium Salts. — When the gas ammonia, NH S , or its 
solution in water, is brought together with acids, salts are 
formed. Thus ammonia and hydrochloric acid give a salt 
of the composition NH 4 C1; ammonia and nitric acid give 
NH 4 N0 3 ; ammonia and sulphuric acid give (NH 4 ) 2 S0 4 . 
These salts are formed according to the following equations: 

NH 3 +H01 =NH 4 01; 
NH 3 + HN0 3 = NH 4 NO a ; 
2NH 3 + H 2 S0 4 = (NHJ 2 S0 4 . 

The salts thus formed are much like the salts of sodium 
and potassium. The only way to compare them with the 
salts of the metallic elements is by assuming that in them 
the part represented by NH 4 acts the part of the metal. 
It is called ammonium, and the salts are called ammonium 
salts. Ammonium has never been obtained in the uncom- 
bined state, as instead of it ammonia is always formed. 

Experiment 108. — Place near each other two vessels, one con- 
taining a little strong hydrochloric acid, and the other a little 
strong ammonia. Explain what you see. 

Ammonium Chloride, OT3 4 C1. — This salt is commonly 
called sal-ammoniac* At present its principal source is 



THE POTASSIUM FAMILY. 175 

the gas-works. When heated it is converted into vapor 
without melting, and with very slight decomposition. 

Experiment 109. — On a piece of platinum-foil or porcelain 
heat a little ammonium chloride. What is the result ? 

[What takes place when ammonium chloride is treated 
with caustic soda? With lime?] 

Ammonium Sulphide, (NH 4 ) 2 S. — This salt, which is made 
by treating ammonia with hydrogen sulphide, is extensively 
used in making chemical analyses. 

Relations between the Atomic Weights of the Alkali 
Metals. — The atomic weight of lithium, which is a metal 
belonging to the potassium family, is 7. Between this and 
the atomic weights of sodium, 23, and potassium, 39, ex- 
ist relations similar to those which exist between the atomic 
weights of chlorine, bromine, and iodine; and of sulphur, 
selenium, and tellurium. [What is this relation?] 

Flame Reactions. — When a piece of clean platinum wire 
is held for some time in the flame of the Bunsen burner, it 
then imparts no color to the flame. If now a small piece 
of sodium carbonate or any other salt of sodium be put in 
it, the flame is colored intensely yellow. AH sodium com- 
pounds have this power, and hence the chemist makes use 
of the fact for the purpose of detecting the presence of 
sodium. Similarly, potassium compounds color the flame 
violet. 

Experiment 110. — Prepare some pieces of platinum wire, 8 to 
10 cm. long, with a small loop on the end. After thoroughly 
cleaning them, insert one in a little sodium carbonate, and notice 
the color it gives to the flame. Try another with potassium car- 
bonate. 

To Separate Two or More Colors. — While it is an easy 
matter to recognize potassium alone, or sodium alone, it is 



176 THE ELEMENTS OE CHEMISTRY. 

not so easy to do so when they are together in the same 
compound. The intense yellow caused by the sodium com- 
pletely masks the more delicate violet caused by the potas- 
sium, so that the latter cannot be seen by the unaided eye. 
In this particular case we can get over the difficulty by let- 
ting the light pass through a blue glass, or a thin vessel 
filled with a solution of indigo. The yellow light is thus 
cut off, while the violet light passes through and can be 
recognized. 

The Prism and the Spectrum. — A better method for de- 
tecting what a light is made of is by means of a prism. 
Lights of different colors are turned out of their course 
to different extents when passed through a prism, as is 
seen in the case of sunlight. A narrow beam of white 
light passing in emerges as a band of various colors, called 
its spectrum. It is thus seen that white light is made of 
different-colored lights. Similarly, we can determine what 
any light is composed of. Every light has its characteris- 
tic spectrum. The light produced by burning sodium, or 
by introducing a sodium compound in a colorless flame, 
has a spectrum consisting of a narrow yellow band. The 
spectrum of potassium consists mainly of two bands, one 
red and one violet. Further, these bands always occupy 
definite positions relatively to one another, so that, in 
looking through a prism at the light caused by potassium 
and sodium, the yellow band of sodium is seen in its posi- 
tion, and the two potassium bands in their positions. 

The Spectroscope. — The instrument used for the purpose 
of examining the spectra of different lights is called the 
spectroscope. It consists essentially of a prism and two 
tubes. Through one of the tubes the light to be examined 
is allowed to pass so as to strike on the prism. The light 



THE POTASSIUM FAMILY, 177 

emerges from the other side of the prism, and is observed 
through the other tube, which is provided with lenses for 
the purpose of magnifying the spectrum. By means of 
the spectroscope it is possible to detect the minutest quan- 
tities of some elements, and, since it was devised, several 
new elements have been discovered through its aid, as, for 
example, caesium, rubidium, thallium, indium, and gallium. 
12 



178 THE ELEMENTS OF CHEMISTRY. 



CHAPTEE XX. 

THE CALCIUM FAMILY: CALCIUM, BARIUM, 
STRONTIUM. 

Calcium, Ca {At. Wt. 40). — This is the principal mem- 
ber of the family. It is widely distributed in nature and 
in enormous quantities; principally as carbonate, CaC0 3 , 
in the form of limestone, marble, and chalk; as sulphate, 
CaS0 4 , in the form of gypsum ; as phosphate, Oa s (P0 4 ) 2 , 
in phosphorite and apatite; as fluoride, CaF 2 , in fluor-spar. 

The element is not easily made. It acts upon water just 
as sodium and potassium do. 

Compounds of Calcium. — The principal compounds of 
calcium with which we have to deal are the chloride, CaCl 2 ; 
the oxide, or quicklime, CaO; the hydroxide, or slaked 
lime, Ca0 2 H 2 ; the hypochlorite, Ca(001) 2 ; the carbonate, 
Ca00 3 ; the sulphate, CaS0 4 ; the phosphate, Oa 3 (P0 4 ) 2 ; 
and the silicates, in the form of glass. 

Calcium Chloride, Ca01 2 . — The property which gives 
this salt its value is its power to absorb water. It is used 
as a drying agent. Gases are passed through it for the 
purpose of drying them, and it is also placed in vessels in 
which it is necessary that the atmosphere should be kept 
dry. 

Experiment 111. — Dissolve 10 to 20 grams of limestone or 
marble in ordinary hydrochloric acid. Evaporate to dryness. 
Expose a few pieces of the residue to the air. — Does it become 
moist? In what experiments has calcium chloride been used, 






THE CALCIUM FAMILY, 179 

and for what purposes ? What would happen if sulphuric acid 
were added to calcium chloride? Try it. Explain what takes 
place. Is the residue soluble or insoluble in water ? 

Calcium Oxide, CaO. — This is the substance commonly 
called lime. It is made by heating calcium carbonate, 
which is decomposed into lime and carbon dioxide: 

CaC0 3 = CaO + C0 2 . 

Limekilns are large furnaces in which limestone and 
other forms of calcium carbonate are heated and converted 
into lime. 

Lime is a white substance which does not melt. When 
heated in the flame of the compound blow-pipe, it gives 
forth an intense light, as any other infusible substance 
would under the same circumstances. When exposed to 
the air, it attracts moisture and carbon dioxide,, and is 
thus converted into the carbonate. This change is called 
air-slaking, and lime thus changed is said to be air- 
slaked. 

Calcium Hydroxide, Ca0 2 H 2 . — When calcium oxide or 
quicklime is treated with water it becomes hot and crum- 
bles to a fine powder. The substance which is formed in 
this operation is somewhat soluble in water, the solution 
being known as lime-zvater. 

Slaking. — The action which takes place when lime is 
treated with water is called slaking. It is represented by 
the equation 

CaO + H 2 = CaO a H 2 . 

The oxide is converted into the hydroxide or hydrate. 

Experiment 112. — To 40 or 50 grams good quicklime add 
100 cc. water. What takes place ? Afterwards dilute to 2 to 3 



180 THE ELEMENTS OF CHEMISTRY, 

litres and put the whole in a wide-stoppered bottle. The un- 
dissolved lime will settle to the bottom, and in the course ot 
some hours the solution above will become clear. Carefully pour 
off some of the clear solution. What takes place when some of 
the solution is exposed to the air? When the gases from the 
lungs are passed through it ? When carbon dioxide is passed 
through it? What takes place when dilute sulphuric acid is 
added to lime-water? Is calcium sulphate difficultly or easily 
soluble in water ? Has lime-water an alkaline reaction ? What 
reaction would you expect to take place between lime and nitric 
acid? 

Calcium Hypochlorite, Ca(OCl) 2 , has already been treated 
of sufficiently under the head of Chlorine. It need only 
be repeated that the form in which chlorine is transported 
is " Meacliing-powder" or "chloride of lime" This is a 
compound containing calcium hypochlorite and calcium 
chloride, 0a(0Cl) 2 + CaCl 2 , which is made by passing chlo- 
rine into slaked lime* 

20a(OH) 2 + 4C1 = Ca(OCl) 2 + CaCl 2 + 2H 2 0. 

v v ' 

Bleaching-p o wder . 

How Bleaching-powder Gives up Chlorine. — Bleaching- 
powder gives up its chlorine by simple exposure to the air 
in consequence of the action of the carbon dioxide. The 
addition of an acid causes a rapid evolution of chlorine. 

Calcium Carbonate, CaC0 3 . — This salt occurs in nature in 
the well-known forms calc-spar, limestone, marble, and 
chalk. The variety of calc-spar found in Iceland, and 
known as Iceland spar, is particularly pure calcium carbon- 
ate. The salt also forms the principal part of oyster-shells, 
coral, etc. In some caves water containing calcium car- 
bonate in solution drips down, and the salt is deposited in 
the solid form from the solution. Thus there are formed 



THE CALCIUM FAMILY, 181 

hanging pieces, shaped like icicles, and below them reach- 
ing up from the bottom are similar pieces with the pointed 
ends upwards. Those which hang down from above are 
called stalactites, those on the bottom are called stalagmites. 

Calcium Sulphate, Gypsum, CaS0 4 + 2H 7 0. — Gypsum is 
the principal variety of calcium sulphate. When heated 
it loses its water of crystallization and forms a powder 
called plaster of Paris, which has the power of taking up 
water and forming a solid substance. The process of solid- 
ification is known as " setting. v Plaster of Paris is largely 
used in making casts. 

Permanent Hardness of Water. — Calcium sulphate is 
somewhat soluble in water A natural water containing it 
is called a hard water, just as is water which contains cal- 
cium carbonate. The haMness caused by calcium carbon- 
ate is remedied by boiling the water, and is, therefore, 
called temporary hardness, while that which is caused by 
gypsum is not remedied by boiling and is therefore called 
permanent hardixess. Why the water is called hard will be 
explained when the subject of soap is treated. 

How to Improve Hard Water. — Water which holds cal- 
cium carbonate in solution can be made soft by adding a 
little lime to it. This forms insoluble calcium carbonate 
with the carbon dioxide, and, as soon as the carbon di- 
oxide is removed, the calcium carbonate which is in solu* 
tion is precipitated. If the hardness is caused by calcium 
sulphate the addition of a little carbonate of soda will pre- 
cipitate the calcium as calcium carbonate, and sodium sul- 
phate will be left in solution: 

CaS0 4 + Na 2 C0 3 = CaCO, + Na 2 S0 4 . 
[Try these reactions.] 



182 THE ELEMENTS OF CHEMISTRY. 

Gypsum Valuable as a Fertilizer. — The addition of 

gypsum to a soil increases its fertility, and it is therefore 

frequently used by farmers to increase their crops. 

Experiment 113. — Heat some powdered gypsum to about 200° 
in an air-bath. Examine what is left and see whether it will be- 
come solid when mixed with a little water so as to form a paste. 
See whether gypsum itself will act in the same way. 

Calcium Phosphate, Ca 3 (P0 4 ) 2 . — The normal phosphate 
in which all the hydrogen of phosphoric acid is replaced 
by calcium is found in nature as phosphorite, and in com- 
bination with calcium fluoride or chloride as apatite. Fur- 
ther, it is the chief earthy constituent of bones, and is 
found in large quantity in bone-ash. 

Calcium Phosphate as a Fertilizer. — Plants need phos- 
phoric acid for their growth, and hence it must be present 
in the soil if the plants are to flourish. Ordinary normal 
calcium phosphate is not soluble, and is therefore not easily 
taken up by the plants. It can be rendered soluble by 
adding sulphuric acid to it, and then it is readily used by 
the plants. 

Superphosphate of Lime. — Normal calcium phosphate 
which has been treated with a certain proportion of sul- 
phuric acid forms the valuable artificial fertilizer known as 
superphosphate of lime. This is a mixture of the phos- 
phate Ca (H 2 P0 4 ) 2 and calcium phosphate formed thus* 

Oa,(P0 4 ) 1 +2H J S0 4 = 20aS0 4 + Ca(H 2 P0 4 ) 2 . 



Superphosphate of lime. 

Mortar. — Mortar is made of slaked lime and sand. 
When this mixture is exposed to the air, carbonate of cal- 
cium is slowly formed, and the mass becomes extremely 
harb. The water contained in the mortar soon passes oil. 



THE CALCIUM FAMILY. 183 

but nevertheless freshly-plastered rooms remain moist for 
a considerable length of time. This is due to the fact that 
a reaction is constantly taking place between the carbon 
dioxide and calcium hydroxide in which calcium carbonate 
and water are formed, 

Ca0 2 H 2 + CO. = CaC0 3 + H 3 0, 

and it is the water thus set free which keeps the air moist. 
The complete conversion of the lime into carbonate re- 
quires a very long time, because the carbonate which is 
formed on the surface tends to protect the lime in the in- 
terior. The hardening may be promoted by keeping up 
fires of coke or charcoal and allowing the product of com- 
bustion to escape into the rooms. 

Glass. — Common glass is a silicate of calcium and so- 
dium, made by melting together sand (silicon dioxide, 
Si0 2 ) with lime, or calcium carbonate, and sodium carbon- 
ate. When potassium carbonate is used instead of sodium 
carbonate the glass is more difficultly fusible. Bohemian 
glass, which is so extensively used in the manufacture of 
chemical apparatus, is a silicate of calcium and potassium. 
Flint-glass } which is especially valuable for the manufac- 
ture of optical instruments, contains lead instead of cal- 
cium It melts much more readily than calcium glass. 

Colored Glass. — Colors are given to glass by putting in 
the fused mass small quantities of various substances. 
Thus a cobalt compound makes glass blue; copper and 
chromium make it green; one of the oxides of copper 
makes it red, etc. 

Compounds of Barium and Strontium. — These closely re- 
semble those of calcium, Barium forms an oxide, BaOj 



184 THE ELEMENTS OF CHEMISTRY. 

corresponding to lime, and also another one known as ba* 
rium dioxide, Ba0 2 . This is formed by passing oxygen 
or air over barium oxide heated to a dull red heat. At a 
higher temperature it gives off the oxygen. These facts 
have recently been taken advantage of for the purpose of 
extracting oxygen from the air. 

Barium Dioxide Used in Making Hydrogen Dioxide. — 
Barium dioxide has already been referred to in describing 
the preparation of hydrogen dioxide, H 2 2 . When it is 
treated with sulphuric acid this reaction takes place: 

Ba0 2 + H 2 S0 4 = H 2 2 + BaS0 4 . 

When it is treated with hydrochloric acid hydrogen di- 
oxide is also formed, thus: 

Ba0 2 -f 2HC1 = H 2 2 + BaCl 2 . 

[Compare this with the reaction which takes place when 
hydrochloric acid acts upon manganese dioxide.] 

Flame Reactions. — Calcium compounds color the flame 
reddish yellow; strontium compounds, intense red; and 
barium compounds, yellowish green. They are frequently 
used for the purpose of producing colored lights. 

Relations between the Atomic Weights. — The atomic 
weight of calcium is 40, that of strontium 87.5, and that 
of barium 137. [Why is this fact of special interest?] 



THE MAGNESIUM FAMILY. 185 



CHAPTER XXI. 

THE MAGNESIUM FAMILY: MAGNESIUM, ZINC, 
CADMIUM, 

THE COPPER FAMILY: COPPER, MERCURY, SILVER. 

Magnesium, Mg {At. Wt. 24). — Magnesium occurs very 
widely distributed in nature, and in considerable quantities. 
Among the important magnesium minerals are magnesite, 
which is the carbonate, MgC0 3 ; dolomite, a carbonate of 
magnesium and calcium; soapstone, serpentine, and meer- 
schaum, which is essentially a silicate of magnesium. 
Further, there are many well-known minerals which contain 
magnesium, as asbestos and hornblende. The element is 
also found in solution in many spring- waters in the form of 
the sulphate, which is known as Epsom salt. 

Preparation of Magnesium.— It is prepared by treating 
magnesium chloride with sodium at a high temperature. 

Properties. — It is a silver- white metal with a high lustre. 
In the air it changes slowly, but it gradually becomes coy 
ered with a layer of the oxide. It burns with a bright 
flame, forming the white oxide. At ordinary temperatures 
magnesium does not decompose water; at 100° it decom- 
poses it slowly. [Compare magnesium with potassium and 
sodium in this respect.] 

Magnesium Oxide, MgO. — This compound is commonly 
called magnesia. A fine white variety is made by heating 
precipitated magnesium carbonate; this is called magnesia 



186 THE ELEMENTS OF CHEMISTRY. 

usta. It is very difficultly soluble in water, forming with 
it magnesium hydroxide, Mg0 2 H 2 , which is practically in- 
soluble in water. [What difference is there between mag- 
nesium and calcium in this respect?] 

Zinc, Zn {At. Wt. 65). — Zinc occurs in nature in combi- 
nation as the carbonate, or calamine, ZnC0 3 , as the silicate, 
and as the sulphide, or zinc blende, ZnS. 

Preparation of Zinc. — It is prepared by mixing the oxide 
with charcoal and heating in earthenware retorts. The 
metal, being volatile, passes over and is condensed. 

Properties of Zinc. — Zinc has very different properties at 
different temperatures. At ordinary temperatures it is 
quite brittle; at 100-150° it can be rolled out in sheets, but 
above 200° it becomes brittle again. In dry air it does not 
change. When heated in the air it takes fire, and burns 
with a bluish flame, forming zinc oxide. It dissolves in all 
the common acids, usually with an escape of hydrogen. 

Uses. — It is used very largely in making batteries. Iron 
covered with a layer of zinc is known as galvanized iron. 
Zinc is one of the constituents of brass, the other being 
copper. German silver consists of brass to which some 
nickel has been added. 

Zinc Oxide, ZnO, is obtained as Flores zmci by burning 
zinc, and by heating the carbonate or nitrate of zinc. It 
turns yellow when heated, but becomes white again on 
cooling. 

Experiment 114. — In a furnace, or in a hot stove fire, heat a 
small sand crucible to a bright red heat. Throw into it pieces of 
zinc. If the temperature is high enough the zinc will boil and 
the vapor will burn with a bright light, and dense white fumes of 
the oxide will be formed. 

Zinc oxide is used as a constituent of paint under the 



THE COPPER FAMILY. 187 

name zinc-white. Lead- white turns black quite readily. 
Zinc-white does not. 

Zinc Sulphate, ZnS0 4 + 7H 2 0. — The common name of 
this salt is tuhite vitriol. It is obtained on the large scale 
by heating zinc sulphide in contact with the air. Under 
these circumstances the sulphide is oxidized: 

ZnS + 40 = ZnS0 4 . 

This operation is known as roasting. By roasting zinc 
sulphide at a higher temperature it is converted into zinc 
oxide: 

ZnS + 30 = ZnO + S0 2 . 

Zinc sulphate is also formed in large quantities in gal- 
vanic batteries and in the preparation of hydrogen. 

Copper, Cu (At. Wt. 63.2). — Copper occurs in nature in 
the uncombined or native state in large quantities in the 
neighborhood of Lake Superior, United States, and in 
Chili. It also occurs in combination with oxygen as ruby 
copper, which is the oxide, Cu 2 0; and with sulphur and 
iron in copper pyrites. 

Preparation of Copper. — Copper is obtained from the 
oxide by heating it with charcoal. [This reduction has 
been illustrated under the head of carbon (see Experiment 
70).] It is also obtained from the sulphides. The chemi- 
cal changes involved are comparatively complicated. 

Properties.— Copper is a hard metal of a reddish color 
and metallic lustre. In dry air it does not change, but in 
moist air it gradually becomes covered with a green layer 
of a carbonate of copper. Mtric acid dissolves it, copper 
nitrate, Cu(N0 3 ) 2 , being formed, and oxides of nitrogen 



188 THE ELEMENTS OF CHEMISTRY. 

evolved [explain the reaction] ; hydrochloric acid does not 
act upon it; sulphuric acid acts when heated with the 
metal; the sulphate, CuS0 4 , is formed and sulphur dioxide 
given off [explain the reaction]. Copper cannot decom- 
pose water, even when water vapor is passed over the metal 
heated to red heat. [Compare with the conduct of the 
members of the potassium, calcium, and magnesium fami- 
lies.] 

Copper-plating. — Copper is precipitated from solutions of 
its salts by zinc, iron, and some other metals, and by an 
electric current. 

Experiment 115. — Into a neutral solution of copper sulphate 
insert a strip of zinc. The zinc will become covered with a layer 
of copper, and zinc will pass into solution as zinc sulphate. The 
zinc simply displaces the copper in this case, as it displaces hy- 
drogen frcm sulphuric acid: 

Zn + CuS0 4 = ZnS0 4 + Cu; 
Zn + H 2 S0 4 = ZnS0 4 4- H 2 . 

Perform a similar experiment, using a strip of sheet-iron in- 
stead of zinc. [What is the result ?] 

The deposition of metallic copper from solutions of its 
salts is extensively used in copper-plating. The object to 
be covered with copper is hung in a solution of copper sul- 
phate and connected with one pole of a galvanic battery, 
the other pole being also in the solution. Decomposition 
takes place, and a layer of copper is deposited on the ob- 
ject. 

Alloys of Copper. — Mixtures of metals made by melting 
them together are called alloys. Brass is an alloy consist- 
ing of about 1 part of zinc and 2 parts of copper. Bell- 
metal and Ironze are alloys of copper and tin. 

Copper Forms Two Series of Salts. — Copper has the power 



THE COPPEB FAMILY 189 

to form two distinct series of compounds,, of which the 
following are examples: 

CuCl, Cu01 2 ; 
CuBr, CuBr,; 
Cu 2 0, CuO. 

Those which belong to the first class, corresponding to the 
chloride, CuCl, are called cuprous compounds. Thus, 
CuOl is cuprous chloride; Cu 2 0, cuprous oxide, etc. On 
the other hand, compounds of the second class are called 
cupric compounds. Thus, CuCl a is cupric chloride; CuO, 
cupric oxide, etc. Mercury, iron, and some other metals 
also form two series of compounds whhh differ from each 
other in much the same way. 

Cuprous Oxide, Cu 2 0, is found in nature as ruby copper, 
and is formed when copper is heated in contact with the 
air. It is a bright-red, insoluble compound. 

Cupric Oxide. CuO, is obtained by heating copjoer to 
redness in contact with the air, or by heating the nitrate. 
It is also formed when caustic soda or potash is added to a 
boiling-hot solution of a copper salt. If the solution is 
cold, blue cupric hydroxide, Cu0 2 H 2 , is precipitated, bui 
this easily loses water, particularly if the solution is heated. 
The reactions which take place are: 

CuS0 4 + 2N"aOH = Cu0 2 H 2 + Na 2 S0 4 , and 
Cu0 2 H 2 = CuO + H 2 0. 

Experiment 116. — Add some caustic soda or potash to a small 
quantity of a cold solution of copper sulphate in a test-tube. 
After noticing the appearance of the precipitate first formed, neat. 
What change takes place ? 



190 TEE ELEMENTS OF CEEMISTBY. 

Copper Sulphate, CuS0 4 + 5H 2 0. — This salt is manu- 
factured on a large scale,, and is commonly known by the 
name " blue vitriol." [What salt is called " white vitriol"?] 
It forms large blue crystals, which, when heated, lose water 
and become colorless. The colorless substance becomes 
blue again in contact with water. 

Mercury, Hg (At. Wt. 200). — Mercury occurs in the un- 
combined state as drops enclosed in rocks, though princi- 
pally in combination with sulphur as cinnabar, HgS. It 
is obtained by roasting cinnabar, when vapors of mercury 
and sulphur dioxide are given off. The mercury is then 
condensed in appropriate vessels. It is a silver- white metal 
of a high lustre. At ordinary temperatures it is liquid, 
though it becomes solid at — 39°. 5. It does not change in 
the air at ordinary temperatures. It is insoluble in hydro- 
chloric acid and cold sulphuric acid. [Try each.] It dis- 
solves in hot concentrated sulphuric acid, and is easily 
soluble in nitric acid. [Try each.] The vapor of mercury 
is very poisonous. 

Amalgams. — With other metals mercury forms alloys 
called amalgams. In ordinary galvanic batteries the zinc 
plates are treated with mercury, and thus covered with a 
layer of zinc amalgam which protects them from the action 
of the acids used. 

Mercuric Oxide, HgO, is the red substance which was 
used in one of the first experiments for the purpose of pre- 
paring oxygen. It is formed when mercury is heated for 
some time near its boiling-point in contact with the air, 
and is made by heating the nitrate. 

Mercurous Chloride, HgCl, is commonly known by the 
name calomel. It is precipitated when a soluble chloride 
or hydrochloric acid is added to a solution of any mercu- 



THE COPPER FAMILY. 191 

rous salt. It is manufactured by subliming an intimate 
mixture of mercuric chloride and mercury: 

HgCl, + Hg - 2HgCl. 

It is a white substance,, insoluble in water, which finds ex- 
tensive application in medicine. 

Mercuric Chloride, HgCl 2 , commonly called corrosive svb- 
hmate, is manufactured on the large scale by subliming an 
intimate mixture of mercuric sulphate and common salt: 

HgS0 4 + 2Na01 = Na 2 S0 4 + HgCl 2 . 

It is a white substance, soluble in water. It is extremely 
poisonous, and prevents the decay of organic substances. 

Silver, Ag (At Wt. 108). — Silver occurs in the uncom- 
bined state or native; in combination with sulphur; and 
with sulphur and other metals. Small quantities of silver 
sulphide are found in almost all varieties of galenite or 
lead sulphide. It occurs more rarely as the chloride, 
bromide, and iodide. 

Extraction of Silver from its Ores.— Much of the silver 
used is obtained from galenite. This mineral is treated in 
such a way as to effect the separation of the lead (see 
Lead), and the silver is separated from sulphur at the 
same time. But it is dissolved in a large quantity of lead, 
and the problem which presents itself to the metallurgist 
is how to separate the small quantity of silver from the 
large quantity of lead. 

PattisorCs Process. — The separation of the silver from 
the lead is accomplished by a process invented by Pattison. 
It consists in melting the mixture and allowing it to cool 



192 THE ELEMENTS OF CHEMISTRY. 

until crystals appear, These are nearly pure lead. They 
are dipped out and the liquid left is again treated in the 
same way. By this means there is finally obtained a pro- 
duct which is rich in silver, but which still contains some 
lead. This is heated in appropriate vessels in contact with 
the air, when the lead is oxidized, while the silver remains 
in the metallic state. This last process is called cupellation. 
Amalgamation Process. — Some ores of silver are treated 
in another way, known as the amalgamation process. The 
ores are mixed with common salt and roasted, when the 
silver is obtained in the form of the chloride. The mass 
is then treated with iron and water, when this reaction 
takes place: 

2A.g01 + Fe = Fe01 2 + 2Ag. 

The mass is next treated with mercury, which forms an 
amalgam with the silver. When this amalgam is taken 
out, dried and heated, the mercury passes over, while the 
silver remains behind. 

Properties of Silver. — Silver is a white metal with a 
high lustre. It is not acted upon by air, oxygen, or water 
at ordinary temperatures. Sulphur acts readily upon it, 
causing it to blacken superficially, the black coating being 
silver sulphide. Silver coins and other articles carried in 
the pockets are apt to become tarnished in consequence of 
the presence of small quantities of sulphur in the perspi- 
ration. 

Alloys of Silver. — The silver which is used for coins and 
most other purposes is an alloy with copper, the pure 
metal being too soft. The alloy usually contains from 7-J 
to 10 per cent of copper. 

Silver-plating. — Objects are covered with silver mostly 



THE COPPER FAMILY. 193 

by connecting them with one pole of an electric battery 
and placing them in a bath containing a silver salt in solu- 
tion, in which the other pole of the battery is also inserted. 
Glass is covered with silver by putting it into a solution 
containing silver together with something which has the 
power to separate the silver in the metallic state when 
heated. Under these circumstances the silver is deposited 
in a smooth, lustrous layer. Mirrors are made in this 
way. 

Silver Nitrate, AgN"0 3 , is known also by the name 
" lunar caustic/' as it has the power to destroy the flesh, 
and is therefore used to burn out wounds. It is prepared 
by dissolving silver in dilute nitric acid. Marks made by 
silver nitrate turn black in the sunlight. Hence this salt 
is used as a constituent of indelible inks. When working 
with silver salts the fingers are apt to become stained. 
These stains and generally any spots made by silver salts 
can be removed by a solution of potassium cyanide, which 
forms soluble salts with compounds of silver.* 

Experiment 117. — Dissolve a ten or twenty-five cent piece in 
dilute nitric acid. What action takes place ? Dilute the solu- 
tion to 200 to 300 cc. with water. What is the color of the solu- 
tion ? What does this indicate ? Does this color prove the 
presence of copper ? Add a solution of common salt until it 
ceases to produce a precipitate. The chemical change which 
takes place is expressed by the equation 

AgN0 3 + NaCl = AgCl + NaNO.. 

Insoluble. 



* Quite recently some scoundrel disfigured the beautiful marble 
statue of the great chemist Liebig which is in Munich by bespatter- 
ing it with a solution of nitrate of silver. The professors of chem- 
istry in the university succeeded, however, in removing the stains 
completely by applying a paste containing potassium cyanide. 
13 " 



194 THE ELEMENTS OF CHEMISTRY. 

The copper nitrate is not changed and remains in solution. 
Filter off the white silver chloride and carefully wash with hot 
water. Dry the precipitate on the filter, by placing the funnel with 
the filter and precipitate in an air-bath heated to about 110°. 
Remove the precipitate from the filter and put it into a porcelain 
crucible. Heat gently with a small flame until the chloride is 
melted. Cut out a piece of sheet-zinc large enough to cover the 
silver chloride. Lay it on the silver chloride. Now add a little 
water and a few drops of dilute sulphuric acid, and let the whole 
stand for twenty -four hours. The silver chloride is changed to 
silver, and zinc chloride is formed: 

Zn + 2AgCl = ZnCl 2 -h 2Ag. 

Take out the piece of zince and wash the silver with a little 
dilute sulphuric acid, and then with water. Dissolve the silver 
in dilute nitric acid and evaporate to dryness on the water-bath, 
so that the excess of nitric acid is driven off. Dissolve the resi- 
due in water, and put the solution either in a bottle of dark glass 
or one wrapped in dark paper. 

Experiment 118. — To a few cubic centimetres of water in a 
test-tube add 5 to 10 drops of the solution of silver nitrate just 
prepared. To this dilute solution add a little of a dilute solution 
of sodium chloride. What takes place ? Place it aside where the 
light can shine upon it, and notice the change of color which 
gradually takes place. In the same way make the bromide by 
adding potassium bromide, and the iodide by adding potassium 
iodide to silver nitrate. 

Photography. — The last experiments showed that the 
chloride, bromide, and iodide of silver are insoluble in 
water and are changed by light. The art of photography 
is based upon the changes which certain compounds, es- 
pecially salts of silver, undergo when exposed to the light. 
A plate of glass is covered with a thin layer of a salt of 
silver. The plate is then exposed in the camera to the 
action of the light from the object to be photographed. 
Where the light acts upon the salt it is changed, while 



THE COPPER FAMILY. 195 

where the light does not act it is not changed. An image 
of the object towards which the plate was directed is thus 
left on the plate. The image must be developed by treat- 
ing the plate with a solution of gallic or pyrogallic acid, 
or a solution of ferrous sulphate. After the image is de- 
veloped, the plate is treated with something which dis- 
solves the unchanged silver salt. The best substance for 
this purpose is a solution of sodium hyposulphite. 



196 THE ELEMENTS OF CHEMISTRY. 



OHAPTEE XXII. 

THE ALUMINIUM FAMILY— THE IRON FAMILY: IRON, 
COBALT, NICKEL. 



Aluminium, Al (At. Wt. 27). — Aluminium is the only 
element of the family which it represents which need be 
considered here. It is an extremely important element 
which occurs very widely distributed in nature. Among 
the many important and widely-distributed minerals which 
contain aluminium are feldspar, granite, mica, and cryolite. 
Clay is essentially a silicate of aluminium. 

Preparation of Aluminium. — Aluminium is prepared by 
treating the chloride with metallic sodium. [How is mag- 
nesium prepared ? How sodium ?] Quite recently a meth- 
od has been devised by which it appears to be possible to 
make aluminium much more cheaply than it has been 
made hitherto. The new method consists in mixing the 
oxide of aluminium with carbon and passing the current 
from a powerful electrical machine through the mixture. 
The apparatus is known as the Oowles electric furnace. 

Properties. — Aluminium has a strong lustre; its color is 
like that of tin. It is very strong and yet malleable. It 
is lighter than most metals in common use, its specific 
gravity being 2.7, while that of iron is 7.8, that of silver 
10.57, and that of tin 7.3. Further, it does not change 



liver 
•e in 



TEE ALUMINIUM FAMILY. 197 

dry or moist air. These properties give it great value, and 
it is only the fact that it cannot be prepared sufficiently 
cheaply from the compounds of aluminium found in 
nature that prevents its wide-spread use. It appears 
probable that in the course of time aluminium will largely 
take the place of iron, as it is certainly better adapted to 
most of the uses to which iron is put. 

Aluminium Oxide, A1 2 3 . — This compound occurs rarely 
in nature in the form of ruby, sapphire, and corundum. 
It is very hard, and as emery, which is powdered corun- 
dum, is used for polishing. It is made artificially by 
heating the hydroxide, A10 3 H 3 : 

2A10 3 H 3 = Al a 3 + 3H,0. 

Alums. — Aluminium sulphate forms complex compounds 
with the sulphates of the alkali metals, all of which crys- 
tallize beautifully. Potassium alum is the best known of 
these. It may be regarded as derived from 2 molecules of 
sulphuric acid, 2H 2 S0 4 = H 4 S 2 8 , by the replacement of 3 
atoms of hydrogen by 1 atom of aluminium, and the fourth 
by 1 atom of potassium; thus, A1KS 9 8 or A1K(S0 4 ) 2 . The 
crystals always contain 12 molecules of water, the complete 
formula being A1K(S0 4 ) 2 -f 12H 2 0. Similarly, sodium 
alum is AlKa(S0 4 ) 2 + 1^H 2 0, and ammonium alum, 
A1NH 4 (S0 4 ) 2 + 12H 2 0. 

Uses of Alum. — Alum and other compounds are used in 
dyeing cotton cloth. Colors do not adhere to cotton fibre 
as they do to wool and silk. On adding aluminium hy- 
droxide or alum to the cotton the dye-stuffs unite with 
these and form insoluble compounds. Substances which 



198 THE ELEMENTS OF CHEMISTRY. 

have the power of combining with dye-stuffs in this way 
are called mordants. Alum is an acid salt and has the 
power of decomposing carbonates. It is therefore some- 
times wrongly used as a constituent of "baking powders" 
in connection with sodium bicarbonate. 

Aluminium Silicates. — The silicate of aluminium occurs 
in nature in enormous quantities, in combination with 
other silicates forming some of the most important min- 
erals. The most abundant of these is ordinary feldspar y 
AlKSi 3 8 . When these silicates are subjected to the influ- 
ence of the air, rain, frost, etc., they suffer decomposition. 
The silicate of the alkali metal dissolves and is washed 
away, while aluminium silicate is partly Jeft behind and is 
also partly washed away. Pure aluminium silicate is 
known as kaoline, and has the composition Al 4 (Si0 4 ) 3 + 
4H 2 0. The impure varieties are called clay. 

Porcelain, etc. — Kaoline is used for making porcelain. 
For this purpose it is mixed with water and moulded into 
the proper shape and then heated to a high temperature 
in a properly-constructed furnace. The ordinary varieties 
of clay are used for making common earthenware vessels 
and bricks. Earthenware and porcelain are glazed in two 
ways: porcelain by coating it with an easily-fusible sub- 
stance and heating to a high temperature; earthenware by 
heating to a strong red heat in a furnace and throwing in 
a quantity of damp salt. The salt is decomposed and 
sodium silicate is formed. This fuses on the surface of 
the vessels and forms a layer which is not porous. 

Ultramarine. — The substance known as lapis lazuli con- 
sists of a silicate of aluminium and sodium, together with 
a sulphide of sodium, The coloring-matter obtained by 



THE IBON FAMILY. 199 

powdering it was formerly expensive, "but it is now made 
artificially by the ton, and the color of the artificially -pre- 
pared substance is even more beautiful than that of the 
natural. It is made by heating a mixture of clay, dry 
sodium carbonate, sulphur, and wood-ashes without access 
of air. 

Aluminium Bronze. — This is an alloy of aluminium and 
copper, containing 10-12 per cent of the former. It is ex- 
tremely hard and very durable, and has many useful appli- 
cations. Its color is similar to that of gold. 

Iron, Fe (At. Wt. 56). — At the present time it is un- 
doubtedly true that iron is the most important metal for 
man. It occurs in the form of magnetite, Fe 3 4 , and hem- 
atite, Fe 2 3 ; as the carbonate, or siderite, FeC0 3 ; in 
combination with sulphur as iron pyrites, FeS 2 ; and as 
silicates and hydrated oxides, or hydroxides. Iron in the 
metallic state is found in the form of meteors or masses 
which fall upon the earth from space. 

Extraction of Iron from its Ores. — The extraction of iron 
from its ores is theoretically simple, the essential steps 
being these: 

(1) The conversion of the ore into the oxides, unless the 
oxides themselves are used. 

This is accomplished by roasting them. If sulphides are 
roasted the sulphur passes off as sulphur dioxide, and the 
iron remains as the oxide. In roasting, further, water is 
driven off, and the carbonate is decomposed into the oxide 
and carbon dioxide. 

(2) Eeduction of the Oxides by means of charcoal or 
coke. 

This is accomplished by mixing the ore with the reduc- 



200 



THE ELEMENTS OF CHEMISTRY. 



ing agent and heating in a blast-furnace. The blast-furnace 

is constructed of fire-brick and 
masonry. It is from 50 to 90 feet 
high, and from 15 to 18 feet wide 
in the widest part. An idea of 
the construction is given by Fig. 
39. Alternate layers of ore and 
fuel are introduced into the top of 
the furnace. A flux is also added. 
This is usually limestone or quick- 
lime. The object of the flux is to 
form a fusible substance with the 
earthy constituents of the ore. As 
the iron is reduced it melts, and 
the compound formed with the flux 
also melts. The molten iron being 
the heavier liquid, it sinks to the 
bottom followed by the other, 
which is called the slag. The iron 
collects in the bottom of the furnace, called the crucible, 
and is drawn off in the liquid condition. 

Pig-iron. — The iron drawn off from the furnace is called 
pig-iron. It is always impure, containing phosphorus, 
sulphur, silicon, and as much as 2 to 6 per cent of carbon. 
It is brittle and easily fusible, and is used for casting, 
being known as cast-iron. 

Wrought-iron. — When the carbon, silicon, and phos 
phorus are removed from pig-iron it becomes very tougl 
and malleable. It is now tvrought-iroji. Oast-iron is con- 
verted into wrought-iron in one of two ways : 

(1) By melting it and blowing air into the molten mass. 




Fig. 39. 






THE IRON FAMILY. 



201 



The carbon, phosphorus, and silicon are thus oxidized and 
gotten rid of. This process is known as puddling. 

(2) By mixing cast-iron with some of the purer ores and 
heating to a high temperature, when the carbon, phos- 
phorus, etc., are oxidized by the oxygen of the ores. 
This process is called cementation. 

Steel. — Steel is a third variety of iron which contains 1 
to 2 per cent of carbon; more than wrought and less than 
cast iron. It has the property of becoming extremely hard 
and brittle when heated and suddenly cooled. When cau- 
tiously heated and allowed to cool slowly it is rendered 
elastic. This process is called tempering. 

There are two ways of making ateel: 

(1) Wrought-iron is heated with charcoal or with iron 
containing carbon. This is known as the cementation pro- 
cess, and is the opposite of the cementation process for 
making wrought-iron. 

(2) Cast-iron is melted in a large vessel called a con- 
verter (see Fig. 40), and then partly 
oxidized by currents of air forced into 
the mass. Oast-iron is now added, and 
steel containing any desired proportion 
of carbon thus made. This is known as 
the Bessemer process. 

Pure Iron. — Pure iron is almost un- 
known. It is a white metal with a 
strong lustre. In moist air it rusts; 
that is, it becomes covered with a layer 
of oxide and hydroxide which is formed 
by the action of the air and water. The Fig. 40. 

wire used for pianos is nearly pure; but if this be dissolved 
in hydrochloric or sulphuric acid, small black particles of 




202 THE ELEMENTS OF CHEMISTRY. 

carbon will remain undissolved. The odor noticed when 
ordinary iron is dissolved in acid is due to the presence of 
impurities. 

Compounds of Iron. — Iron, like mercury and copper, 
forms two series of compounds which differ markedly from 
each other. These are the ferrous and ferric compounds. 
Thus with chlorine it forms two chlorides, one of which, 
ferrous chloride, has the composition expressed by the for- 
mula FeCl 2 ; the other, ferric chloride, by FeCl 3 . It appears 
from a study of the relative weights of these chlorides in 
the state of vapor (see Chapter XIV., page 126) that the 
above formulas should be doubled, so that ferrous chloride 
is now commonly represented by Fe 2 Cl 4 , and ferric chlo- 
ride by Fe 2 Cl 6 . For our purpose the simpler formulas 
will answer just as well. Similarly there are two oxides, 
FeO and Fe 2 3 ; two sulphates, ferrous sulphate, FeS0 4 , 
and ferric sulphate, Fe 2 (S0 4 ) 3 , etc. 

Change of Ferrous to Ferric Compounds. — Ferrous com- 
pounds pass into ferric compounds by simple contact with 
the air; and are readily converted by oxidizing agents, 
such as nitric acid, potassium chlorate, etc. When, for 
example, ferrous hydroxide, Fe(OH) 2 , is exposed to the 
air suspended in water, it changes to ferric hydroxide, 
Fe(OH) 3 . The change is represented by the equation 

2Fe(OH) 2 + H 2 + = 2Fe(OH) 3 . 

So, also, when ferrous chloride is left standing in hydro- 
chloric acid solution it changes to ferric chloride, and the 
change is rapidly effected by boiling with a little nitric 
acid: 

2FeCl 8 + 2HC1 + = 2FeCl 3 + H 3 0. 



THE IRON FAMILY. 203 

Ferrous Chloride, FeCl a , is formed by dissolving iron in 
hydrochloric acid. 

Experiment 11 9. —Dissolve a little iron wire in dilute hydro- 
chloric acid. Hydrogen is evolved, accompanied by small quan- 
tities of other gases whose formation is due to the presence of 
impurities in the iron, and carbon is left undissolved as a black 
residue. To a few drops of the solution in water in a test-tube 
add at once caustic soda. This precipitates ferrous hydroxide, 
Fe(OH) 2 , which changes color rapidly, becoming finally reddish 
brown. Pure ferrous hydroxide is white. As it passes to the 
ferric condition it becomes dirty green, and darker and darker 
until it is reddish brown, which is the color of ferric hydroxide, 
Fe(OH) 3 . Heat another small portion of the solution of ferrous 
chloride to boiling, add two or three drops of concentrated nitric 
acid and boil again. Kepeat this operation two or three times. 
The ferrous chloride is thus oxidized to ferric chloride. It will be 
noticed that the color of the solution after the oxidation is red- 
dish yellow, whereas before the oxidation it was nearly colorless 
or slightly greenish. Add caustic soda to the solution of ferric 
chloride. A reddish-brown precipitate of ferric hydroxide will be 
formed. Just as in this case you have passed from ferrous 
chloride to ferric chloride by oxidation, so you can pass back 
again to the ferrous compouud. Thus, by adding a little zinc to 
a solution of ferric chloride in which hydrochloric acid is present, 
the hydrogen evolved extracts chlorine from the ferric chloride 
and converts it into ferrous chloride: 

FeCl 3 + H = FeCl 2 + HC1. 

Ferrous Sulphate, FeS0 4 + 7H a O.— This salt, which is 
commonly known as "green vitriol" or "copperas/' is 
formed by the action of sulphuric acid on iron. [What is 
" White vitriol "? " Blue vitriol " ?] It is extensively used 
in the preparation of ink and in dyeing. 

Inks. — Iron inks are made by treating solutions of tannic 
acid, which is obtained from nut-galls, with ferrous sul- 
phate or copperas. There are many kinds of ink in use 



204 THE ELEMENTS OF CHEMISTRY. 

which are not made in this way. Printers' ink contains 
lamp-black. So also does India ink. Inferior inks are 
made of aniline dyes, which are made from coal-tar. 

Iron Alum, FeK(S0 4 ) 2 + 12H 2 0, is formed by bringing 
ferric sulphate and potassium sulphate together. It re- 
sembles ordinary alum, A1K(S0 4 ) 2 + 12H 2 0, but differs 
from it in containing iron instead of aluminium. 

Ferric Oxide, Fe 2 3 , occurs in nature in lustrous crystals, 
as hematite, and as a red mass. It is prepared on the large 
scale by heating copperas in the air, when the change rep- 
resented in the following equation takes place: 



2FeS0 4 = Fe 2 3 + S0 3 + S0 2 






The oxide thus obtained is a dark-red powder called 
rouge. ■ It is used for polishing glass and as a paint. 

Ferroso-ferric Oxide, Fe 3 4 , or magnetic oxide of iron, 
is found in nature in the form of loadstone. It is formed 
when iron is burned in oxygen (see Experiment 26). 

The sulphides of iron have been repeatedly mentioned. 

Ferrous Sulphide, FeS, is made by heating sulphur and 
iron together in proper proportions. It is used in making 
hydrogen sulphide. [Explain how.] 

Iron Pyrites, FeS 2 , is a yellow crystallized substance 
very abundantly found in nature. When heated in a 
closed tube sulphur is given off. When heated in an open 
vessel as upon a shallow iron pan or spoon, the sulphur is 
oxidized to sulphur dioxide, and the iron is left in the 
form of the oxide. [Verify these statements by experi- 
ment.] 

Nickel, M {At. Wl. 58.5), is found in meteoric iron and 
in combination with arsenic. It forms two series of salts 



THE IRON FAMILY. 205 

corresponding to the two hydroxides nickelous hydroxide, 
Ni(OH) 2 , and nickelic hydroxide, Ni(0H) 3O Nickel is 
used for making coins, and for plating other metals. It is 
not acted upon by the air. 

Cobalt, Co {At. Wt. 59.1), is found in combination with 
arsenic and sulphur, and also in small quantities accom- 
panying nickel in meteoric iron. 

Cobalt compounds are used on account of their colors* 
Smalt is made by fusing glass with a cobalt compound, 
when a blue mass is obtained which is powdered and used 
as a paint. When cobaltic oxide and aluminium oxide are 
fused together a dark-blue substance is formed which is 
known as cobalt ultramarine. 



206 THE ELEMENTS OF CHEMISTRY. 



CHAPTER XXIII. 
MANGANESE— CHROMIUM— URANIUM-BISMUTH. 

Manganese, Mn (At. Wt. 55).— Manganese is found in 
nature in the form of the oxides., of which manganese di- 
oxide, or the black oxide of manganese, occurs most abun* 
dantiy. With oxygen it forms the following compounds: 
manganous oxide, MnO; manganic oxide, Mn 2 3 ; manga- 
noso-manganic oxide, Mn 3 4 ; manganese dioxide, Mn0 2 ; 
and permanganic anhydride, Mn 2 7 . 

Manganese presents points of resemblance with aluminium 
and iron. Like iron it forms two series of salts, the man- 
ganous and manganic series, which diJffer from each other 
very much as ferrous and ferric compounds do. 

Chromium, Or (At. Wt. 52.3). — This element is com- 
paratively rare, and occurs almost only in combination 
with oxygen and iron as chromic iron, Fe0r 2 0^ 

Potassium Chromate, K 2 Cr0 4 , is formed when finely- 
powdered chromic iron is heated with potassium carbonate 
and potassium nitrate. 

Potassium Dichromate, K 2 Cr 2 7 . — This is the form in 
which chromium is most frequently met with. It is formed 
from the chromate by adding acetic or nitric acid. The 
change which takes place is represented thus: 

2K f OrO % + 2HN0 3 = 2KN0 3 + K 2 Cr 2 7 + H 2 0. 

The relation between the chromate and the dichromate 
will be more readily understood by considering the acids 



MANGANESE— CHROMIUM— URANIUM— BISMUTH 207 

from which they are derived. These are chromic acid, 
H 2 Cr0 4 , and dichromic acid, H 2 Cr 2 7 . The latter may be 
regarded as derived from the former by loss of water: 

2H 2 Cr0 4 = H 2 Cr 2 7 + H 2 0. 

Experiment 120. — Potassium dichromate is converted into the 
chromate by adding a solution of potassium hydroxide until the 
color becomes pure yellow: 

K 2 Cr 2 7 + 2KOH = 2K 2 Cr0 4 + H 2 0. 

Convert 10 to 20 grams potassium dichromate into the chro- 
mate. Evaporate to crystallization. Compare the salt thus 
obtained with potassium dichromate 

Experiment 121. — Convert the potassium chromate just ob- 
tained into potassium dichromate by adding dilute nitric acid 
until the color is red. Evaporate to crystallization. 

Both the chromate and dichromate are good oxidizing 

agents, 

Experiment 122. — Treat a little of each salt in a test-tube with 
hydrochloric acid. [What evidence do you get that the salts are 
good oxidizing agents ?] 

Chrome-yellow. — The chromates of lead and barium are 

insoluble in water. They are yellow. The lead salt is the 

well-known paint chrome-yellow. 

Experiment 123. — Add a little of a solution of potassium chro- 
mate or dichromate to a solution of barium chloride, and of lead 
acetate or nitrate. 

Chrome Alum is a salt related to ordinary alum, but con- 
taining chromium instead of aluminium. Its formula is 
CrK(S0 4 ) 2 + 12H 2 0. The alums have analogous formulas; 

Ordinary alum , . . . A1K(S0 4 ) 2 + 12H 2 0; 

Iron alum. FeK(S0 4 ) 2 + 12H 2 0; 

Chrome alum CrK(S0 4 ) 2 + 12H a O. 



208 THE ELEMENTS OF CHEMISTBY. 

Uranium, U {At. Wt. 239). — This element occurs mostly 
in the form of the oxide IT 3 4 known as pitchblende. 

Bismuth, Bi {At. Wt. 208), occurs mostly native, and is ob- 
tained by heating the ores and allowing the molten bismuth 
to run out. In appearance it closely resembles antimony. 

Bismuth forms alloys which melt at low temperatures. 
The best known of these is "fusible metal/' which is com- 
posed of lead, tin, and bismuth. 

The chief compound of bismuth and oxygen is the yellow 
oxide Bi 2 3 , which is formed when bismuth is burned in 
the air e 

The principal salt of bismuth is the nitrate Bi(NO s ) 8 + 
5H a O. It is used in medicine. 






LEAD-TIN— PLATINUM-GOLD. 209 



CHAPTER XXIV. 
LEAD— TIN— PLATINUM— GOLD. 

Lead, Pb {At. Wt. 207). — Lead occurs in combination in 
several forms in nature, as, for example, in the sulphate, 
carbonate, chromate, and sulphide. The sulphide, PbS, 
known as galena, or galenite, is the most important ore of 
lead. 

Extraction of Lead from its Ore. — The extraction of lead 
from its ore is accomplished in one of two ways: 

(1) By heating the sulphide with iron, when the latter 
combines with the sulphur, forming iron sulphide, while 
the lead is set free. 

(2) By roasting the sulphide until it is partly converted 
into lead oxide and lead sulphate; then heating the mixture 
without access of * air, when the two reactions take place 
which are represented in these equations: 



PbS + 2PbO =3Pb + SO f ; 
PbS + PbS0 4 = 2Pb + 2S0 2 . 



The lead is thus set free, and the sulphur driven off as 
sulphur dioxide. 

Properties of Lead. — Lead is a bluish-gray metal with a 
high lustre. It is soft and not very strong. It melts at 
about 325°. All lead salts are poisonous. Nitric acid dis- 
solves it, but hydrochloric and dilute sulphuric acids do 
14 



210 THE ELEMENTS OF CHEMISTRY. 

not. It is precipitated in metallic form from a solution of 
one of its salts by metallic zinc. The formation is some- 
times called the " lead-tree" or " Arbor Saturni." 

Experiment 124.— Dissolve 30-40 grams lead acetate (sugar of 
lead) in a litre of water, add a few drops of acetic acid, and put 
the solution in a wide-mouthed bottle. Suspend a piece of sheet- 
zinc in the middle of the solution, and let it stand. The lead will 
be deposited slowly in crystallized form. At the same time the 
zinc will pass into solution. The zinc simply takes the place of 
the lead: 






Zn + Pb(N0 3 ) 2 = Zn(N0 3 ) 2 + Pb. 



fre- 



Lead Water-pipes. — Pipes for conveying water are 
quently made of lead, and under most circumstances there 
is no danger in this; but some waters, particularly such as 
are rich in carbon dioxide, act upon lead and dissolve it in 
small quantity. Such waters are exceedingly dangerous. 
If air and water together act upon lead, it is much more 
readily acted upon than when the air is excluded. In 
moist air lead tarnishes. 

Experiment 125. — Cut a piece of sheet-lead an inch or two 
square and partly cover it with water in a shallow dish. Allow 
it to stand for several days, renewing the water from time to time. 
Then filter off and examine the solution to see whether there is 
any lead in solution. This is done by taking advantage of the 
fact that lead chloride is difficultly soluble, and lead sulphate and 
sulphide insoluble, in water. (1) To a little of the solution in a 
test-tube add a few drops of hydrochloric acid. Is a precipitate 
formed? (2) To another small portion of the solution add a few 
drops of sulphuric acid. Is a precipitate formed? (3) Into a 
third portion pass a little hydrogen sulphide. What change takes 
place ? Try the same experiments with a very dilute solution of 
lead acetate. 

Oxides of Lead. — Lead forms three compounds with oxy- 
gen, viz.: lead suboxide, Pb 2 0; lead oxide, PbO; and load 



LEAD— TIN— PLA TINUM—GOLD. 211 

peroxide, Pb0 2 . Red lead, or minium, is apparently a 
mixture of the oxide and peroxide, and has approximately 
the composition Pb 3 4 . 

Lead Oxide, PbO, is commonly known by the name lith- 
arge. It is formed by the oxidation of molten lead in con- 
tact with the air. In the separation of lead from silver 
advantage is taken of this fact. Silver does not combine 
with oxygen when heated in the air. Therefore when a 
mixture of lead and silver is heated in the air to the proper 
temperature the lead is converted into the oxide, while the 
silver remains unchanged. The lead oxide thus formed is 
easily separated from the silver. 

Minium, Red Lead, Pb 3 4 (= 2PbO + PbO,).— When 
litharge is heated in the air to 400° it takes up oxygen and 
is converted into minium, or red lead. When minium is 
heated to a high temperature it gives up oxygen and is 
again converted into yellow lead oxide. Treated with ni- 
tric acid, a part is dissolved, forming lead nitrate, while 
lead peroxide, a brown powder, remains behind. 

Experiment 126. — Treat a little minium with ordinary dilute 
nitric acid, and note the change in color. Does lead pass into 
solution ? How do you know ? 

Lead Peroxide, Pb0 2 , conducts itself somewhat like man- 
ganese dioxide. When treated with hydrochloric acid 
chlorine is evolved: 

Pb0 2 + 4HC1 = PbCl, + 2H 2 + 201. 

Experiment 127.— Treat a little lead peroxide with hydrochloric 
acid in a test-tube. In what form is the lead after the experiment ? 
Is the product soluble or insoluble in water ? 

The sulphate, chromate, and chloride have already been 
referred to. They are formed by adding a soluble sulphate, 



212 THE ELEMENTS OF CHEMISTRY. 

chromate, and chloride to a solution of a lead salt. The 
chromate is the well-known chrome-yellow. 

Lead Carbonate, PbC0 3 , is the well-known and much- 
used pigment white lead. The objection to its use in a 
laboratory is that it turns black in the presence of even 
small quantities of hydrogen sulphide. Zinc-white does 
not act in this way, as zinc sulphide is a white substance. 

Tin, Sn (At. Wt. 118). — Tin occurs in nature mostly as 
tin-stone ? which is the oxide Sn0 2 . The metal is obtained 
from the ore by reducing with charcoal. It is a white metal 
which resembles silver in appearance. It is soft and mal- 
leable, and can be hammered out into very thin sheets, 
forming the well-known tin-foil. At 200° it is brittle; and 
at 228° it melts. It does not change in the air at ordinary 
temperatures. Ordinary concentrated nitric acid oxidizes 
it, the product being a compound of tin, oxygen, and hy- 
drogen, known as metastannic acid, ^ which is a white pow- 
der insoluble in nitric acid and in water. 

Extraction of Tin from its Ore. — The oxide or tin-stone is 
pulverized, mixed with charcoal, and heated in a furnace, 
when the tin appears in the molten condition. 

Uses of Tin. — Owing to the fact that tin does not change 
in the air it is used as a covering for other metals. Ordi- 
nary tin-ware is made of sheets of iron covered with tin. 
An inferior variety of tin- ware is manufactured containing 
lead. If such ware is used for cooking-utensils or for making 
cans for preserving fruit and vegetables serious results may 
follow, as the acids of the foods may dissolve enough lead to 
form poisonous liquids. Copper covered with tin is also 
used for various purposes, as for bath-tubs and pins. 

Alloys of Tin. — Among the valuable alloys containing tin 
are solder, which consists of tin and lead j britannia, 



LEAD— TIN— PLATINUM— GOLD. 21 3 

which consists of 9 parts of tin and 1 part of antimony; 
bronze and bell-metal, which consist of tin and copper. 

Soldering. — Soldering in general is any process by which 
metals are made to adhere by means of other metals added 
in the molten condition. Ordinary soldering consists in 
joining metals together by means of a solder consisting of 
about equal parts of lead and tin. In order that the solder 
may hold it is necessary that the surfaces of the metal to 
which it is applied should be bright. This is brought 
about by the use of resin or by washing with a little acid and 
then adding some borax, which in the molten condition dis- 
solves any metallic oxides which may be present, leaving the 
surfaces bright. There is some danger in the use of solder 
for tin cans, as it is possible for the contents to get in con- 
tact with the solder unless the work is done with unusual 
care. 

Stannous and Stannic Compounds. — Tin forms two classes 
of compounds, the stannous and stannic compounds. These 
do not bear to each other the same relation as that which 
exists between cuprous and cupric compounds, or that be- 
tween ferrous and ferric compounds. In stannous com- 
pounds the tin appears to be bivalent, as indicated by 
the formulas Sn01 2 , SnO, SnS, which respectively repre- 
sent stannous chloride, oxide, and sulphide. In stan- 
nic compounds, on the other hand, the tin appears to be 
quadrivalent, as indicated by the formulas SnCl 4 , Sn0 2 , 
SnS 2 , which respectively represent stannic chloride, oxide, 
and sulphide. 

Stannous Chloride, SnCl 2 , and Stannic Chloride, SnCl 4 , 
are the most used compounds of tin. They find application 
in dyeing. The former is known as tin-salt. It is made by 
dissolving tin in hydrochloric acid. 



214 THE ELEMENTS OF CHEMISTRY. 

Stannic Sulphide, SnS 2 , is a yellow substance used under 
the name mosaic gold as a pigment in decorating. 

Platinum, Pt {At. Wt. 194.8.), occurs almost always 
accompanied by the rare metals iridium, palladium, and os- 
mium, in the form of alloys. The ore is found in the 
Ural Mountains, in California, Australia, and a few other 
places. It is prepared by treating the ore with strong 
aqua regia, which dissolves the platinum, together with 
some iridium. The platinum chloride thus obtained is 
precipitated by means of ammonium chloride, with which, 
as with potassium chloride, it forms a difficultly soluble 
compound, (NH 4 ) 2 PtCl 6 . When this is heated to a suffi- 
ciently high temperature it is decomposed, leaving me- 
tallic platinum behind. 

Properties of Platinum. — Platinum is a grayish-white 
metal with a high lustre. Its specific gravity is 2L15, it 
being one of the heaviest substances known , The specific 
gravity of iron is 7.8, that of lead 11.4. In other words, a 
piece of platinum weighs nearly three times as much as a 
piece of iron of the same dimensions, and nearly twice as 
much as a piece of lead of the same dimensions. Platinum 
is not dissolved by hydrochloric, nitric, or sulphuric acid ; 
but aqua regia dissolves it, forming platinum chloride, 
Pt01 4 . Fusing caustic alkalis attack it ; sodium carbon- 
ate does not. It does not change in the air, and does not 
melt except in the flame of the oxyhydrogen blow-pipe. 
It resists the action of most substances. 

Uses of Platinum. — The properties of platinum make it 
extremely valuable to the chemist. Platinum crucibles 
and evaporating-dishes, foil, and wire are in constant use 
in every laboratory, and it is difficult to see how we could 
get along without them. Large retorts of platinum are 



LEAD— TIN— PLA TINUM— G OLD. 216 

used for the purpose of concentrating sulphuric acid and 
distilling it. 

Gold, Au (At. Wf. 196.7). — Gold usually occurs native. 
It is found enclosed in quartz, or more frequently in quartz 
sand. It is separated mechanically by washing, and then 
extracted with mercury, which forms an amalgam with it. 
The amalgam is afterwards heated, when the mercury 
passes oyer and the gold remains behind. 

Properties of Gold. — Gold is a yellow metal with a high 
lustre. It is quite soft and extremely malleable. It can 
be beaten into leaves not more than y^-J^ of a millimetre 
thick. Its specific gravity is 19.3. It combines directly 
with chlorine, but not with oxygen. Hydrochloric, nitric, 
and sulphuric acids do not act upon it ; but aqua regia 
dissolves it, forming gold chloride. On account of the 
fact that gold resists the action of other substances it was 
formerly spoken of as the Icing of metals, and therefore 
the mixture of hydrochloric and nitric acids which dis- 
solves it was called aqua regia, or royal water. 

Uses of Gold. — Gold ware and coin are made of an alloy 
of gold and copper. The standard gold coin of the United 
States contains nine parts of gold to one of copper. The 
composition of gold for jewelry is usually stated in carats. 
Pure gold is 24-carat gold ; 20-carat gold contains 20 parts 
gold and 4 parts copper ; 18-carat gold contains 18 parts 
gold and 6 parts copper, etc. 



236 THE ELEMENTS OF CHEMISTS F. 



CHAPTEK XXV. 
SOME FAMILIAR COMPOUNDS OF CARBON. 

Organic Chemistry. — When the compounds which are 
obtained from plants and animals were first studied it was 
supposed that they were entirely different in every way 
from the compounds obtained from earthy or mineral sub- 
stances. The former were called organic substances, for 
the reason that they were obtained from organized beings ; 
while the latter were called inorganic substances. Organic 
substances were the subject of Organic Chemistry, and inor- 
ganic substances formed the subject of Inorganic Chemis- 
try. These names are still in use, though they have lost 
their original meaning. Organic Chemistry means now 
only the Chemistry of the Compounds of Carbon. 

Occurrence of the Compounds of Carbon. — The most widely 
distributed compound of carbon is carbon dioxide, which, 
as you have learned, is the starting-point of all life on the 
globe. All living things are formed from it either directly 
or indirectly. The substances which exist in the vegeta- 
ble kingdom in largest quantity are cellulose and starch; 
but besides these a very large number of other substances 
are found, as the sugars, — the alkaloids of which, mor- 
phine, quinine, and nicotine, are examples, — oxalic acid, 
malic acid, tartaric acid, citric acid. In the animal king- 
dom, too, occur many substances, as albumin, fibrin, etc. 

Formation of the Compounds. — Certain natural processes 






COMPOUNDS OF CARBON. 217 

which are not throughly understood have giyen rise to the 
formation of a complex mixture of organic compounds, 
principally hydrocarbons, in petroleum (page 106). 

Distillation of Coal. — The destructive distillation of coal 
for the purpose of making illuminating-gas, and the forma- 
tion 3f coal-tar, have already been referred to. Coal-tar is 
one of the most important sources of compounds of car- 
bon. The hydrocarbons benzene, C 6 H 6 , toluene, C 7 H 8 , 
xylene, C 8 H 10 , naphthalene, C 10 H 8 , anthracene, C 14 H 10 , 
etc., are obtained from this source. 

Distillation of Wood. — Wood is heated in closed vessels 
mostly for the purpose of making charcoal, as already ex- 
plained. Among the products obtained from this source 
are ivood-spirit, or methyl alcohol, and pyrolig neons acid, 
or acetic acid. Large quantities of acetic acid are pre- 
pared in this way. 

Distillation of Bones. — In order to make bone-black, 
bones are subjected to destructive distillation. The oil 
which passes over is collected and known as bone-oil. Of 
late this has proved to be the source of a large number of 
compounds which are of special interest on account of 
their connection with the valuable alkaloids, quinine, mor- 
phine, etc. 

Fermentation. — A number of the most important com- 
pounds of carbon are formed by a process known as fer- 
mentation. This is a general term meaning any process in 
which a chemical change is effected by means of minute 
animal or vegetable organisms. The best known example 
of fermentation is that of sugar, which gives rise to the 
formation of ordinary alcohol. 

Classes of Compounds of Carbon. — The chief classes of 
these compounds are the hydrocarbons, some of which have 



218 



THE ELEMENTS OF CHEMISTRY. 



already been treated (see pages 107); the alcohols; the 
acids; the ethers; and the ethereal salts. First a few of 
the best known examples of each of these classes will be 
taken up, and afterwards some other familiar compounds 
which do not belong to any one of these classes. 



Alcohols. 

Methyl Alcohol, Wood-spirit, 0H 4 0. — This is formed by 
the distillation of wood, and is separated from the other 
products which are formed at the same time. It has, 
when pure, a pleasant odor and taste and acts upon the 
animal system very much as ordinary alcohol does. It 
burns without giving light or smoke, and may therefore be 
used in lamps for heating purposes as ordinary alcohol is. 
It is used in the manufacture of varnishes. 

Ethyl Alcohol, Spirits of Wine, C 2 H 6 0.— This well- 
known substance is formed by the fermentation of grape- 
sugar or glucose. 

Experiment 128. — Dissolve 20 to 30 grams commercial grape- 
sugar, or 20 to 30 cc. table sy- 
rup, in 1 to 2 litres of water 
in a flask. Connect the flask 
by means of a bent glass tube 
with a cylinder or bottle con- 
taining clear lime-water. The 
vessel containing the lime-water 
must be provided with a cork 
with two holes. Through one 
of these passes the tube from 
the fermentation-flask; through the other a tube connecting with 
a vessel containing solid caustic potash, the object of which is to 
prevent the air from acting upon the lime-water. The arrange- 
ment of the apparatus is shown in Fig. 41. Now add to the so- 
lution of grape-sugar or syrup a little fresh brewer's yeast; close 
the connections and allow to stand. Soon an evolution of gas 




Fig. 41. 



COMPOUNDS OF CABBOJST. 219 

will begin, and, as this passes through the lime-water, a precipi- 
tate will be formed which can be shown to be calcium carbonate. 

What Change takes place in the Sugar ? — If the solution 
in the flask is examined carefully it will be found to contain 
alcohol and no sugar. Grape-sugar has the composition 
expressed by the formula C 6 H 12 6 . By fermentation it is 
decomposed, forming alcohol, C 2 H 6 0, and carbon dioxide, 
C0 2 . The decomposition is expressed by the equation 



C 6 H 12 6 = 2C 2 H 6 + 2C0 2 



What Causes the Change ? — It has been found that the 
change of grape-sugar is caused by small organized bodies 
which grow in the solution. These bodies are contained 
in ordinary yeast. 

Germs in the Air. — When fruit-juices which contain 
sugar are exposed to the air they undergo fermentation 
without the addition of yeast. This is due to the fact that 
the germs or seeds of the bodies which cause fermentation 
are everywhere 'floating in the air. Hence, when a liquid 
in which these seeds can grow is exposed to the air, the 
bodies are formed, and fermentation takes place. 

Different Kinds of Fermentation. — The fermentation 
which yields alcohol is only one of many kinds. Among 
the others are: (1) lactic-acid fermentation, which takes 
place in the souring of milk; and (2) acetic-acid fermenta- 
tion, which causes the transformation of alcohol into acetic 
acid. The latter ferment is contained in " mother of 
vinegar." 

Distillation of Fermented Liquids. — In order to get the 
alcohol from liquids which have undergone fermentation 
they must be distilled. For this purpose very perfect 



'220 THE ELEMENTS OF CHEMISTRY. 

forms of stills have been devised, so that the alcohol passes 
over nearly free from other substances. Usually it con- 
tains impurities known ^ fusel oil. 

Properties of Alchol. — Pure ethyl alcohol has a peculiar, 
pleasant odor. It remains liquid at very low temperatures, 
but has recently been converted into a solid at a tempera- 
ture of — 130.5°. It burns with a flame which does not 
deposit soot, and was hence formerly much used in labora- 
tories for heating purposes, and is still used where gas can- 
not be obtained. Its effects upon the human system are 
well known. It intoxicates when taken in dilute form, 
while in large doses it is poisonous. It lowers the temper- 
ature of the body when taken internally, although it 
causes a sensation of warmth. 

Uses of Alcohol. — Alcohol is the principal solvent for or- 
ganic substances. It is hence extensively used in the arts, 
as in the manufacture of varnishes, perfumes, and tinctures 
of drugs. The many beverages in use owe their intoxicat- 
ing power to the presence of alcohol. The milder forms 
of beer contain from 2 to 3 per cent;, light wines about 8 
per cent; while whiskey, brandy, etc., sometimes contain 
as much as 60 to 75 per cent. 

Glycerin, C 3 H 8 3 . — Glycerin is an alcohol which occurs 
very widely distributed as a constituent of fats. The rela- 
tion it bears to the fats will be explained when the acids 
which enter into the fats are taken up. It is obtained from 
the fats by boiling them with an alkali like caustic soda or 
caustic potash, or by heating with steam. 

Properties. — Glycerin is a thick, colorless liquid with a 
sweetish taste. It attracts moisture from the air, and is 
hence used to keep surfaces moist. 



COMPOUNDS OF CARBON- 221 



Acids. 

Formic Acid, CH 2 2 . — This acid occurs in nature in red 
ants, in stinging-nettles, in the shoots of some of the vari- 
eties of pine, and elsewhere. It is a colorless liquid. 
Dropped on the skin, it causes extreme pain and produces 
blisters. 

Acetic Acid, C 2 H 4 2 . — This is the acid contained in vine- 
gar which gives to it its value. It is formed from alcoholic 
liquids by exposing them to the air, in consequence of the 
presence of a microscopic organism which is contained in 
what is commonly known as "mother of vinegar." The 
formation of acetic acid from alcohol is due to the action 
of oxygen as represented in the equation 

C 2 H 6 + 0, = 2 H 4 2 + H.O. 

Alcohol. Acetic acid. 

But oxygen alone does not effect the change. When the 
ferment is present the oxidation takes place. Acetic acid 
is also obtained by distilling wood. Hence the names 
pyroligneous acid and wood-vinegar. 

Properties. — Acetic acid is a clear, colorless liquid. It 
has a very penetrating, pleasant, acid odor, and a sharp 
taste. The pure substance acts upon the skin like formic 
acid, causing pain and raising blisters. 

Uses.- — Acetic acid is extensively used, chiefly in the 
dilute form known as vinegar. It is used in calico-print- 
ing in the form of iron and aluminium salts. With iron it 
gives hydrogen, which is needed in the manufacture of cer- 
tain compounds used in making dyes. 

Salts of Acetic Acid. — The best-known salts of acetic acid 



222 THE ELEMENTS OF CHEMISTRY. 

are lead acetate, Pb (0 2 H 3 2 ) 2 , commonly called sugar of 
lead; and copper acetate, Ou (0 2 H 3 2 ) 2 , a variety of which 
is known as verdigris. 

Fatty Acids. — Formic and acetic acids are the first mem- 
bers of an homologous series (see page 108). Some of the 
more important members are named in the following table: 

Formic acid CH 2 2 . 

Acetic " C2ELO2. 

Propionic " CsH 6 2 . 

Butyric " dHsO.,. 

Palmitic " Ci 6 H 32 2 . 

Stearic " Ci 8 H 86 2 . 

They are called fatty acids for the reason that many of 
them are obtained from fats. 

Butyric Acid, C 4 H 8 2 , is of special interest because it is 
obtained from butter by boiling with caustic potash. It 
occurs also in many other fats. There is a lutyric-acid 
ferment contained in putrid cheese which has the power of 
converting sugar into butyric acid. 

Palmitic Acid, 16 H 32 2 , is obtained from many fats., but 
palm-oil is especially rich in it. 

Stearic Acid, C 18 H 36 2 , is the acid contained in the fat 
known as stearin. The so-called "stearin candles" are 
made of a mixture of palmitic and stearic acids. 

Soaps. — Soaps are the alkali salts of the acids contained 

in fats, especially of palmitic and stearic acids. Fats are 

compounds of these acids with glycerin. When the fats 

are boiled with an alkali, as caustic soda, the corresponding 

salts of the acids are formed, while the glycerin is set free. 

The palmitate and stearate of potassium and sodium are 

the soaps. 

Experiment 129. — In an iron pot boil a quarter of a pound of 
lard with a solution of 40 grams caustic soda in 250 cc. of water 



COMPOUNDS of carbon: 223 

for an hour or two. After cooling add a strong solution of 
sodium chloride. The soap formed will separate and rise to the 
top of the solution, where it will finally solidify. Dissolve some 
of the soap thus obtained in water. 

Use of Soap. — The cleansing power of soap depends upon 
the fact that it dissolves the oily film on the surface of the 
skin and thus facilitates the removal of the foreign sub- , 
stances commonly known as dirt. 

Action of Soap on Hard Waters. — As has been explained, 
a hard water is one which contains salts in solution. 
Temporary hardness is that which is caused by calcium 
carbonate held in solution in the water by carbon dioxide. 
Permanent hardness is caused by calcium sulphate or mag- 
nesium salts. The calcium and magnesium salts of pal- 
mitic and stearic acids are insoluble in water. Therefore, 
when soap is added to a hard water these insoluble salk 
are precipitated, and give the water a hard feeling. In 
attempting to wash the hands with soap in a hard water 
they become covered with a thin layer of the insoluble salts 
which prevents them from rubbing freely over each other, 
and makes them feel sticky. Before the soap can do any 
good all the lime-salt must be precipitated. The action in 
the case of temporary hardness is represented by the equa- 
tion 

2Na0 16 H 31 O a + CaC0 3 = Ca(C 16 H 3I 2 ), + Na,C0 3 . 

Soap. Calcium palmitate. 

In the case of permanent hardness it is represented by 
the equation 

2NaC l6 H 31 2 + CaS0 4 = Ca(C 16 H 31 2 ), + Na,S0 4 . 

Experiment 130. — Make some hard water by passing carbon 
dioxide through dilute lime-water until the precipitate first formed 



224 THE ELEMENTS OF CHEMISTRY. 

is dissolved again. Filter. Make a solution of soap by shaking 
up a few shavings of soap with water. Filter. Add the solution 
of soap to the hard water. Is a precipitate formed ? Rub a piece 
of soap between the hands wet with the hard water. 

Experiment 131. — Make some hard water by shaking a litre or 
two of water with a little powdered gypsum. Perform with it the 
same experiments as those first performed with the water contain- 
ing calcium carbonate. 

Relations of the Soap Industry to other Industries. — A 

great chemist and philosopher has said that the quantity of 
soap used in a country is a measure of the civilization of 
the country. Certain it is that soap is only used by 
civilized people, and that by them it is used in enormous 
quantities. In many farm-houses a primitive method for 
the manufacture of soap is practised, consisting in treating 
refuse fats with the lye extracted from wood-ashes. A soft 
soapy mass is thus obtained known as " soft-soap." Fats 
form the starting-point in the manufacture of all soap. 
These are generally treated with caustic soda. Caustic 
soda is all made from sodium carbonate by the action of 
lime ; and, as you have learned, sodium carbonate is made 
from common salt mostly by the Leblanc process, which 
requires sulphuric acid. Thus the manufacture of sul- 
phuric acid and sodium carbonate is intimately related to 
the manufacture of soap. 

Oxalic Acid, C 2 H 2 4 . — This acid occurs very widely dis- 
tributed in nature, as in the sorrels, which owe their acid 
taste to the presence of acid potassium oxalate, KC 2 H0 4 ; 
and as the ammonium salt in guano. It is probably one of 
the first substances formed from carbon dioxide in the plant. 
It is manufactured by heating wood shavings or sawdust 
with caustic soda and caustic potash. Oxalic acid is an 






COMPOUNDS OF CARBOK 225 

active poison. It is used in calico-printing, and in clean- 
ing brass and copper surfaces. 

Lactio Acid, C 3 H 6 3 . — Lactic acid is made by the fer- 
mentation of sugar by means of the lactic-acid ferment. 
The reaction effected by the ferment is represented by the 
equation 

C 6 H 12 6 = 2C 3 H 6 0, 

Malic Acid, C 4 H 6 5 . — This acid is very widely distributed 
in the vegetable kingdom, as in apples, cherries, etc. 

Tartaric Acid, C 4 H 6 6 . — Tartaric acid occurs very widely 
distributed in fruits, sometimes uncombined, sometimes in 
the form of the potassium or calcium salt; as, for example, 
in grapes, berries of the mountain-ash, potatoes, cucum- 
bers, etc., etc. It is prepared from " cream of tartar." 
This is acid potassium tartrate, which is formed when 
grape-juice ferments. 

Citric Acid, C 6 H 8 7 . — Citric acid, like malic and tartaric 
acids, is very widely distributed in nature in many varieties 
of fruit, especially in lemons. It is also found in currants, 
whortleberries, raspberries, gooseberries, etc., etc. It is 
prepared from lemon-juice: 100 parts of lemons yield 5^ 
parts of the acid. It is a solid, crystallized substance, sol- 
uble in water. It is frequently used for the purpose of 
making lemonade without lemons, and there is no objection 
to its use for this purpose. 

Ethees. 

Ether, C 4 H :o O. — Ordinary ether is the best-known repre- 
sentative of the class of compounds called ethers. It is 

formed from ordinary alcohol by treating it with sulphuric 
15 



226 THE ELEMENTS OF CHEMISTRY. 

acid and distilling. The result of the action which takes 
place is represented by the equation 

2C,H 6 = C 4 H 10 + H 2 0. 

Alcohol. Ether. 

Ether is a liquid which boils at a low temperature and 
takes fire and burns readily. Inhaled it produces insensi- 
bility to pain. It is therefore called an ancesthctic. 

Ethereal Salts. 
Action of Acids upon Alcohols. — When an acid acts upon 
an alcohol it is neutralized, though not as readily as when 
it acts upon a base. The product is a substance which re- 
sembles a salt and is called an ethereal salt. Thus when 
nitric acid acts upon alcohol this reaction takes place: 

2 H 6 + HN0 3 = O.H.NO, + H 2 0. 

The product C 2 H 5 lSr0 8 , called ethyl nitrate, is an ethereal 
salt. The alcohol acts as if it were a substance like caus- 
tic potash and made up thus, C 2 H 5 .OH. The resemblance 
between its action and that of caustic potash is shown by 
the equations 

KOH + HN0 3 = KNO3 + H 2 0, and 
C 2 H 6 OH + HNO3 = O.H.NO, + H 2 0. 

Saponification. — When an ethereal salt is boiled with a 
caustic alkali it is decomposed, the products being an alco- 
hol and an alkali salt. Thus when ethyl nitrate is boiled 
with caustic potash, potassium nitrate and alcohol are 
formed: 

C a H,NO s -f KOH = C 2 H 6 OH f KNO, 



COMPOUNDS OF CARBON-. 227 

This process is called saponification, because the most 
important example is furnished by soap-making. 

Fats. — The fats are ethereal salts in the formation of which 
glycerin, as the alcohol, and three acids take part. The 
three acids are palmitic and stearic acids, already mentioned, 
and oleic acid, C 18 H 34 2 . Although the composition of 
these substances is comparatively complex, the way they act 
upon one another is simple, and is the same as the action 
of nitric acid upon alcohol in forming ethyl nitrate. The 
fats, then, are the palmitate, stearate, and oleate of glyceryl, 
which bears to glycerin very much the same relation that 
ethyl, C 2 H 5 , bears to alcohol. When a fat is boiled wit-i 
caustic soda, then, the sodium salts of the acids, contained 
in the fat, and glycerin are formed. 

Butter consists of ethereal salts of glycerin and sev- 
eral fatty acids, among which are palmitic, stearic, and bu- 
tyric acids. Oleo-margarin is an artificial butter made 
from other fats than that from milk. 

Ethereal Salts as Essences. — The ethereal salts generally 
have pleasant odors, and it is to their presence that many 
fruits owe their flavors. Some of the compounds are now 
made artificially and used instead of the natural extract of 
the fruit. Thus the ethyl salt of lutyric acid is used 
under the name of essence of pineapples, and the amyl salt 
of valeric acid under the name essence of apples. 

Nitroglycerin.— Among the more important ethereal 
salts of glycerin are the nitrates. Two of these are known, 

(O.N0 2 

viz., the mono-nitrate, C 3 H 5 \ OH , and the tri-nitrate, 

(OH 

C 3 H 5 (0 . N0 2 ) 3 , the latter being the chief constituent of 

nitroglycerin. Nitroglycerin is prepared by treating gly- 



228 THE ELEMENTS OF CHEMISTRY. 

cerin with a mixture of concentrated sulphuric and nitric 
acids. It is a pale yellow oil which is insoluble in water. 
At — 20° it crystallizes in needles. It explodes very vio- 
lently by concussion. It may be burned in an open vessel, 
but if heated above 250° it explodes. Dynamite is infu- 
sorial earth* impregnated with nitroglycerin. Nitrogly- 
cerin is the active constituent of a number of explosives. 

Eelatioks between the Compounds Considered. 

Comparison of the Formulas. — On comparing the formu- 
las of the hydrocarbons of the marsh-gas series (see page 
107) with those of the simplest alcohols and the fatty 
acids, it will be seen that these compounds are all related 
in a simple way. Below are lists of a few of the hydro- 
carbons, alcohols, and acids: 



Hydrocarbons. 


Alcohols. 




Acids. 


CH 4 


CH 4 




ch 2 o 2 


C 2 H 6 


2 H 6 




C 2 H 4 2 


C 3 H 8 


C 3 H 8 




c 3 h 6 o 2 


C 4 H 10 , etc. 


C 4 H 10 O, 


etc. 


C 4 H e 2 , etc 



Each of these series is an homologous series. 

Alcohols. — Alcohols have been shown to be derived from 
the hydrocarbons by the replacement of one or more hydro- 
gen atoms by oxygen and hydrogen, OH, or from water 
by replacing one of the hydrogen atoms of the water by a 
compound of carbon and hydrogen. An alcohol, then, is 
a hydroxide, just as a metallic base is; only, instead of con- 

*That is to say, earth made up of the microscopic flinty shells 
which constitute the fossil remains of certain minute and simple 
plants. 



COMPOUNDS OF CABBON. 229 

sisting of a metal in combination with hydrogen and 
oxygen, it consists of a compound of carbon and hydrogen 
in combination with hydrogen and oxygen. Thus: 

Metallic Bases. Alcohols. 

K(OH) CH 3 (OH) 

Na(OH) C 2 H 5 (OH) 

More Complex Alcohols. — Just as lime is a more complex 
base than caustic potash, as shown by the formulas KOH 
and Ca0 2 H 2 or Ca(OH) 2 , so there are more complex alco- 
hols than ordinary alcohol. A good example is furnished 
by glycerin, C 3 H 8 3 , which has been shown to be a hydrox- 
ide corresponding to aluminium hydroxide, Al(OH) 3 , a 
fact which is represented by the formula C 3 H.(OH) 3 . It 
may be called glyceryl hydroxide, the complex, C 3 H B , be- 
ing known as glyceryl. 

Radicals or Residues. — The compounds of hydrogen and 
carbon contained in the alcohols are called radicals or resi- 
dues. So we may say that an alcohol is water in which 
half of the hydrogen has been displaced by a radical. 

HOH 2 H 5 OH 

Water. Ordinary alcohol. 

HOH ( OH 

HOH 3 H 5 \ OH = C 3 H 8 3 . 

HOH ( OH 

Water. Glycerin. 

Acids. — Just as the alcohols have been shown to be de- 
rived from water, so the organic acids have been shown to 
be derived from carbonic acid. Carbonic acid itself is not 
known. But the carbonates are derived from an acid of 

the formula H 8 C0 3 , or CO -J qtt. If, in this acid, a hy- 



230 THE ELEMENTS OF CHEMISTRY. 

droxyl be replaced by a radical, as, for example, by ethyl, 

(OH 
2 H & , a substance of the formula CO -J qW 5 or C 3 H 6 2 is 

the result. If methyl, CH 3 , be introduced in place of 

ethyl, the product is CO -J qjt 3 or C 2 H 4 2 , which is acetic 

acid. In a similar way all the organic acids are derived 
from carbonic acid. 



COMPOUNDS OF CARBON. 231 



CHAPTEK XXVI. 
OTHER COMPOUNDS OF CARBON. 

The Carbohydrates. — The carbohydrates form an im- 
portant group of carbon compounds which include the 
most abundant substances found in the vegetable kingdom. 
They contain, besides carbon, hydrogen and oxygen in the 
proportions to form water. Hence they are called carbo- 
hydrates. The chief compounds included under this head 
are grape-sugar or glucose, cane-sugar, starch, cellulose, 
gum, and dextrin. 

Grape-sugar, Glucose, Dextrose, B H 12 6 . — Dextrose oc- 
curs very widely distributed in the vegetable kingdom, 
particularly in sweet fruits. It is found also in honey and, 
further, in the liver and the blood. 

Formation of Dextrose. — Dextrose or glucose is formed 
from several of the carbohydrates by boiling with dilute 
mineral acids, or by the action of ferments. Its forma- 
tion from cane-sugar takes place according to this equa- 
tion, equal quantities of dextrose and levulose being 
formed: 

0„H„0 11 + H 2 = C.H.,0. + C 6 H I2 6 . 

Cane-sugar. Dextrose. Levulose. 

Its formation from starch is represented by this equa- 
tion: 

6 H 10 O 6 + H 2 O = C 6 H 12 O, 

Starch. Dextrose. 



232 THE ELEMENTS OF CHEMISTRY. 

Manufacture of Dextrose or Glucose. — Dextrose is pre 
pared on the large scale from corn-starch in the United 
States, and from potato-starch in Germany. The change 
is usually effected by boiling with dilute sulphuric acid, 
The acid is afterwards removed by treating with chalk, and 
filtering. [Explain how this removes the acid.] The 
filtered solutions are evaporated either to a syrupy consis- 
tency, and sent into the market under the names " glu 
cose," " mixing-syrup/' etc., or to dryness, the solid pro- 
duct being known as " grape-sugar. " 

Properties. — Dextrose crystallizes from concentrated so- 
lutions, and as seen in commercial "granulated grape- 
sugar " looks very much like granulated cane-sugar. It 
is sweet, but not as sweet as cane-sugar. It is estimated 
that the sweetness of dextrose is to that of cane-sugar as 
3 : 5. Under the influence of yeast it ferments } T ielding 
mainly alcohol and carbon dioxide. Putrid cheese trans- 
forms it into lactic acid, and then into butyric acid. 

Levulose (Fruit-sugar), C 6 H 12 6 . — This form of sugar 
occurs with dextrose in fruits; and is formed by the action 
of dilute acids or ferments on cane-sugar, which breaks up 
according to the equation 

M H„O n + H 2 = C 6 H 12 6 + C 6 H 12 6 . 

Cane-sugar. Dextrose. Levulose. 

As cane-sugar is found in unripe fruits, it is probable 
that the change represented in the equation takes place 
during the process of ripening. 

Cane-sugar, C 12 H 22 O n . — This well-known variety of sugar 
occurs very widely distributed in nature — in sugar-cane, 
sorghum, the Java palm, the sugar-maple, beets, madder- 



COMPOUNDS OF CABBON. 233 

root, coffee, walnuts, hazel-nuts, sweet and bitter almonds; 
in the blossoms of many plants, etc., etc. 

Sugar-refining. — Sugar is obtained mainly from the 
sugar-cane and beets. In either case the processes of ex- 
traction and refining are largely mechanical. When sugar- 
cane is used, this is macerated with water to dissolve the 
sugar. Thus a dark-colored solution is obtained. This is 
evaporated, and then passed through filters of bone-black 
by which the color is removed. The clear solution is then 
evaporated in open vessels to some extent; and, finally, in 
large closed vessels called " vacuur:i-pans," from which the 
air is partly exhausted, so that the boiling takes place at a 
lower .temperature than would bo required under the ordi- 
nary pressure of the atmosphere. The mixture of crystals 
and mother-liquors obtained from the "vacuum-pans" is 
freed from the liquid by being brought into the "centrifu- 
gals." These are funnel-shaped sieves which are revolved 
rapidly, the liquid being thus thrown by centrifugal force 
through the openings of the sieve, while the crystals re- 
main behind and are thus nearly dried. The final drying 
is effected by placing the crystals in a warm room. 

Molasses. — The mother-liquors obtained from the " cen- 
trifugals" are further evaporated, and yield lower grabes of 
sugar; and, finally, a syrup is obtained which does not 
crystallize. This is molasses. 

Properties of Sugar. — Sugar crystallizes from water in 
large well-formed prisms. When heated to 210° to 220°, 
cane-sugar loses water, and is converted into a substance 
called caramel, which is more or less brown in color. When 
boiled with dilute acids, cane-sugar is split into equal parts 
of dextrose and levulose. The mixture of the two is called 
invert-sugar. Yeast gradually transforms cane-sugar into 



234 THE ELEMENTS OF CHEMISTBY. 

dextrose and levulose, and these then undergo fermenta- 
tion. Cane-sugar does not ferment. 

Sugar of Milk, Lactose, C ia H aa O n + H 2 0.— This sugar 
occurs in the milk of all mammals. It is obtained in the 
manufacture of cheese. Cows' milk consists of water, ca- 
sein, butter, sugar of milk, and a little inorganic material, 
in about the following proportions: 

Water.. 87 percent. 

Casein 4 " 

Butter 3£ " 

Sugar of milk 4f " 

Mineral matter f " 

100 

Cheese is made by adding rennet to the milk, which 
causes the separation of the casein. The sugar of milk re- 
mains in solution, is separated by evaporation, and puri- 
fied by recrystallization. It has a slightly sweet taste, and 
is much less soluble in water than cane-sugar. 

Souring of Milk. — Sugar of milk ferments under certain 
circumstances, and is transformed mostly into lactic acid. 
The souring of milk is a result of this fermentation. The 
lactic acid formed coagulates the casein j hence the thick- 
ening. 

Cellulose, 6 H 10 O 5 . Cellulose forms, as it were, the 
groundwork of all vegetable tissues. It presents different 
appearances and different properties, according to the 
source from which it is obtained ; but these differences are 
due to substances with which the cellulose is mixed ; and 
when they are removed, the cellulose left behind is the 
same thing, no matter what its source may have been 
The coarse wood of trees and the tender shoots of the 

-•'"-*-•■■— "-•'-'- - 



: 



COMPOUNDS OF CARBON. 235 

ton-wool, hemp, and flax consist almost wholly of cellu- 
lose. 

Properties. — Cellulose does not crystallize, and is insol- 
uble in all ordinary solvents. It dissolves in concentrated 
sulphuric acid. If the solution be diluted and boiled, the 
cellulose is converted into dextrin and dextrose. It will 
thus be seen that rags, paper, and wood, all of which con- 
sist largely of cellulose, might be used for the preparation 
of dextrosa or glucose, and consequently of alcohol. 

Gun-cotton, Pyroxylin, Nitro-celluose. — Cellulose has 
some of tie properties of alcohols; among them the power 
to form ethereal salts with acids. Thus, when treated with 
nitric acid it forms several nitrates, just as glycerin forms 
the nitrates known as nitro-glycerin (which see). The 
nitrates are explosive, and are used for blasting under the 
name gun-cotton. 

Collodion. — A solution of gun-cotton in a mixture of 
ether and alcohol is known as collodion solution, which is 
much used in photography. When poured upon any sur- 
face, such as glass, the ether and alcohol rapidly evaporate, 
leaving a thin coating of the nitrates. 

Celluloid. — Celluloid is an intimate mixture of gun-cot- 
ton and camphor. As it is plastic at a slightly elevated 
temperature, it can easily be moulded into any desired 
shape. When cooled it hardens. 

Paper. — Paper in its many forms consists mainly of cel- 
lulose. The essential features in the manufacture of paper 
are, first, the disintegration of the substances used. This 
is effected partly mechanically and partly by boiling with 
caustic soda. Then the resulting mass is converted into 
ptilp by means of knives placed on rollers. The pulp, 
with the necessary quantity of water, is then passed be- 



236 THE ELEMENTS OF 0HEMI8TBZ 

tween rollers. Chiefly rags of cotton or linen are used in 
the manufacture of paper; wood ^nd straw are also used. 

Starch, C 6 H 10 O 5 . — Starch is found everywhere in the 
vegetable kingdom in large quantity, particularly in all 
kinds of grain, as maize, wheat, etc. ; in tubers, as the po- 
tato, arrowroot, etc.; in fruits, as chestnuts, acorns, etc. 

Manufacture of Starch. — In the United States starch is 
manufactured mainly from maize; in Europe, from pota- 
toes. The processes made use of are mostly mechanical. 
The maize is first treated with warm water; the softened 
grain is then ground between stones, a stream of water 
running constantly into the mill. The thin paste which 
is carried away is brought upon sieves of silk bolting-cloth, 
which are kept in constant motion. The starch passes 
through with the water as a milky fluid. This is allowed 
to settle when the water is drawn off. The starch is next 
treated with water containing a little alkali, the object of 
which is to dissolve gluten, oil, etc. The mixture is now 
brought into shallow, long wooden runs, where the starch 
is deposited, the alkaline water running off. Finally, the 
starch is washed with water, and dried at a low tempera- 
ture. 

Properties. — Starch in its usual condition is insoluble in 
water. If ground with cold water it is partly dissolved. 
If heated with water the membranes of the cells of which 
the starch is composed are broken, and the contents form a 
partial solution. On cooling, it forms a transparent jelly 
called starch-paste. By dilute acids and ferments starch 
is converted into dextrin, maltose, and dextrose. 

Flour. — Wheat flour, which may serve as an example of 
flour in general, contains water, starch with a little sugar 
and gum, gluten, and a small quantity of mineral matter. 



COMPOUNDS OF CARBON. 237 

The finest flour contains about 10 per cent of gluten and 
70 per cent of starch. Gluten is a substance which re- 
sembles in many respects the white of eggs, or egg-albu- 
min. 

Bread-making. — The chemical changes which take place 
in bread-making are of special interest. Bread is made by 
mixing the flour with water and a little yeast. The dough 
thus prepared is put in a warm place for a time, when it 
rises. The rising is a result of fermentation caused by the 
yeast. A part of the starch contained in the flour is con- 
verted into sugar, and this is then converted into alcohol 
and carbon dioxide by fermentation. The alcohol passes 
off for the most part, and the carbon dioxide in striving to 
escape from the thick gummy dough fills the mass with 
bubbles of gas, making the mass light and porous. When 
the loaf is put into the oven the gases contained in it ex- 
pand, making it still lighter; then the fermentation ]s 
checked and no further chemical change takes place except 
on the surface, where the substances are partly decomposed 
and converted into a dark-colored product, the crust, 

A Few Compounds from Coal-tab. 

Aromatic Compounds. — The fact that benzene, C fc H 6 , 
toluene, C 7 H g , and other hydrocarbons are obtained from 
coal-tar has already been mentioned (p. 217). These hy- 
drocarbons are the starting-points for the preparation of a 
very large number of compounds of carbon which are com- 
monly called the "aromatic compounds/'' as many of them 
have a pleasant aromatic odor. 

Nitrobenzene, C 6 H 6 N0 2 . — This substance is formed by 
treating benzene with nitric acid: 



238 THE ELEMENTS OF CHEMISTRY. 

C 6 H 6 + HN0 8 = C.H.NO + H,0. 

It is a yellow liquid which has a pleasant odor like that of 
the oil of bitter almonds. It is much used under the name 
artificial oil of bitter almonds. 

Aniline, C^H.NH,. — When nitrobenzene is treated with 
any solution from which hydrogen is given off the oxygen 
is extracted and replaced by hydrogen : 

C 8 H 6 N0 2 + 6H = C e H 6 NH 2 + 2H 5 0. 

The product is the substance known as aniline. It is a 
colorless liquid. When treated with mercuric chloride 
(corrosive sublimate, HgCl 2 ) or arsenic acid it is con- 
verted into the dye magenta, which is the substance from 
which the aniline dyes are prepared. 

Aniline Dyes. — Of these a large number are in use. 
They are all derivatives of rosaniline, of which magenta is 
a salt. A great many different colors of aniline dyes are 
made, some of them of great beauty. 

Phenol, Carbolic Acid, C 6 H 6 0. — This familiar substance 
is contained in coal-tar, and is extracted from it by treat- 
ing with caustic soda in which the carbolic acid dissolves. 
When pure it crystallizes in beautiful colorless rhombic 
needles. It has a peculiar, penetrating odor, and is poi- 
sonous. It is much used as a disinfectant. 

Oil of Bitter Almonds, 



, C„H tt O. — This substance occurs 
Benzoic Aldehyde, 

in combination with amygdalin, which is found in bitter 

almonds, laurel-leaves, cherry-kernels, etc. Amygdalin 

belongs to the class of compounds known as glucosides, 

which break up into glucose and other substances. Amyg- 



COMPOUNDS OF CARBON 239 

dalin itself, under the influence of emulsin, which oc- 
curs with it in the plants, breaks up into oil of bitter al- 
monds, hydrocyanic acid, and dextrose : 

C 20 H 2 ,NO U + 2H 2 = C,H 6 + CNH + 2C 6 H I2 f . 

Amygdalin. Oil of Hydrocy- Glucose, 

bitter anic acid, 

almonds. 

It is prepared from bitter almonds, which yield about 1.5 
to 2 per cent, It is a liquid which has a pleasant odor. 
It is made artificially from coal-tar, and is used in the 
preparation of artificial indigo. 

Benzoic Acid, C 7 H 6 2 . — Benzoic acid occurs in gum ben- 
zoin and in the balsams of Peru and Tolu, and is made ar- 
tificially from coal-tar by oxidizing toluene,* C 7 H 8 . 

Balsams and Odoriferous Resins. — The balsams of Peru 
and Tolu are thick fragrant fluids which are obtained from 
certain trees in South America and elsewhere by cutting the 
bark. Benzoin is a similar substance. These as well as 
myrrh, frankincense, and other substances of the kind are 
used for their odors. The odors are increased when the 
substances are heated. Hence they are largely used as in- 
cense. 

Gallic Acid, 7 H 6 5 . — Gallic acid occurs in sumach, in 
Chinese tea, and many other plants. It is formed by boil- 
ing tannin or tannic acid with sulphuric acid. It is pre- 
pared from gall-nuts by fermentation of the tannin con- 
tained in them. It is closely related to tannin or tannic 
acid. 

Tannic Acid, Tannin, 14 H O 9 . — This substance occurs 

* The name toluene conies from the fact that this hydrocarbon was 
first obtained from the balsam of Tolu. 



240 TEE ELEMENTS OE CHEMISTRY. 

in gall-nuts, from which it is extracted in large quantities. 
It is soluble in water. Its solution gives a dark blue-black 
color with iron salts. Tannin is used extensively in medi- 
cine, in dyeing, in the manufacture of leather and of ink. 

Experiment 132. — Boil 10 grams of powdered gall-nuts with 
60 cc. of water, adding water from time to time. A solution of 
tannin is thus obtained. Filter after standing. In a test-tube 
add to some of this solution a few drops of a solution of copperas 
(ferrous sulphate). A colored precipitate is formed which gradu- 
ally changes to black. 

Tanning. — The process of tanning consists in treating 
hides from which the hair has been removed with an in- 
fusion of hemlock or oak bark, or of sumach leaves, in 
which there is tannic acid. The acid combines with certain 
parts of the hides, forming insoluble compounds which 
remain in the pores, converting the hides into leather. 

Indigo. — In several plants which grow in the East and 
West Indies, in South America, Egypt, and other warm 
countries, there occurs a substance called indican which, 
when treated with dilute mineral acids and certain fer- 
ments, breaks up into indigo-blue and a substance resem- 
bling glucose. Commercial indigo contains as its princi- 
pal ingredient indigo-blue. Indigo-blue is now prepared 
artificially by first making the oil of bitter almonds from 
coal-tar and further transforming this by complicated pro- 
cesses. 

Naphthalene, C 10 H 8 . — This is a hydrocarbon which is 
contained in coal-tar in large quantity. It is a beautiful 
white crystallized substance much used in the preparation 
of dyes. 

Anthracene, ]4 H 10 . — Anthracene like naphthalene is ob- 
tained from coal-tar. Its chief use is in the preparation 
of artificial alizarin. 



COMPOUNDS OF CABBON. 241 

Alizarin, C 14 H 8 4 . — Alizarin is the well-known dye 
which is obtained from madder-root. For some years it 
has been made artificially from anthracene, and the culti- 
vation of madder has been largely given up. Madder-root 
was used for dyeing "Turkey red." Artificial alizarin is 
almost exclusively "used for this purpose at present. 



Glucosides. — Glucosides are substances which occur in 
nature in the vegetable kingdom, and which break up un- 
der the influence of ferments and dilute acids into sugar 
and other compounds. Amygdalin has already been men- 
tioned. This breaks up into oil of bitter almonds and 
dextrose. Indican, which yields indigo and dextrose, is 
another example. 

Myronic Acid, another glucoside, is found in the form of 
the potassium salt in black mustard-seed. When treated 
with myrosin, which is contained in the aqueous extract of 
white mustard-seed, potassium myronate is converted into 
dextrose and oil of mustard. 

Alkaloids.— These are compounds occurring in plants, 
frequently being those parts of the plants which are most 
active when taken into the animal body. They are hence 
sometimes called the active principles of plants. Many of 
these substances are used in medicine. They all contain 
nitrogen and in some respects resemble ammonia. Only a 
few of the more important alkaloids need be mentioned 
here. 

Quinine. — This valuable alkaloid is obtained from the 
outer bark of certain trees which grow in Peru. The 
bark is known as Peruvian bark. There is some hope that 
quinine will be prepared artificially before long. 



242 THE ELEMENTS OF CHEMI8TBT. 

Cocaine is found in cocoa-leaves. Its hyc ,chloric-acid 
salt has recently come into prominence in medicine, owing 
to the fact that a small quantity of its S0x .xon placed 
upon the eye or the gums or injected beneath the skin 
causes insensibility to pain. 

Nicotine occurs in tobacco-leaves in combination with 
malic acid. 

Morphine and Narcotine are the principal alkaloids found 
in opium, which is the evaporated sap that flows from in- 
cisions in the capsules of the white poppy before they are 
ripe. 



QUESTIONS AND PROBLEMS. 

CHAPTER I. 

What two kinds of changes are you familiar with? 

Give some familiar illustrations of each. 

What is the chief difference between the two kinds of change? 

Mention some examples of physical changes which are not given in 
the book. 

Mention some examples of chemical changes not given in the book. 
Why do you call these changes chemical changes? 

What is meant by saying that physical and chemical changes are 
related? 

Give some familiar examples which make these relations clear. 

How does the steam-engine illustrate these relations? 

Suppose a stone should fall upon some gunpowder and cause it to 
explode, which would be physical and which chemical change? 

Give some examples showing that heat can cause chemical changes. 

Give some examples showing that chemical changes can produce 
heat. 

Give examples showing that in some cases when substances are 
simply brought together chemical changes are caused. 

Give some examples showing that solution aids chemical action. 

How can we distinguish chemical action from all other kinds of 
action? 

What is the difference between a mixture and a chemical compound? 

How can this difference be illustrated by means of iron and sul- 
phur? 

Suppose sugar and sand were placed together in a vessel and well 
shaken up, would a chemical compound or a mechanical mixture be 
formed? Try the experiment, and see whether you can answer the 
question with the aid of the experiment. Treat the substance with 
water ; what takes place? What is left? 

When iron and sulphur combine chemically, is there any gain or 
loss in weight? 

Explain the difference between elements and compounds. 

Is wood an element? Why? 

Is the number of compounds larger than the number of elements? 

How many elements enter into the composition of the things with 
which we generally have to deal? 



244 THE ELEMENTS OF CHEMISTRY. 

Give some examples of elements. Why are they called elements? 

Give some examples of compounds. Why are they called com- 
pounds? 

In general, what is meant by chemical action? 

What three kinds of chemical action are there? Give examples of 
each. 

Why does a stone fall to the earth when thrown upward? 

Why do substances act chemically upon one another? 

Suppose chemical attraction should cease, what would be the result? 

Which of the elements is most abundant? Which comes next in 
order? 

Which is the principal element that enters into the composition 
-of living things? 

How are the Dames of the elements formed? Give examples. 

What is meant by the symbols of the elements? 

CHAPTER II. 

Describe the changes which are produced in lead, zinc, and tin by 
heating them, and describe the experiments which taught you what 
these changes are. 

How did you learn that the air had anything to do with these 
changes? 

Did heat have anything to do with the changes? Suppose you 
knew that the bits of metal used in Experiments 13, 14, and 15 in- 
creased in weight when heated in the air, and that they did not in- 
crease in weight when heated so that the air could not get at them, 
what would that show ? 

What familiar facts show that the air has something to do with 
burning? 

How could you find out what the air does when things burn in it? 

What is noticed when a candle is burned in a closed vessel ? 

Does a candle in burning gain or lose in weight? 

How much of the air is used up when anything burns in a closed 
vessel? 

Suppose a substance is burned in a closed vessel containing air and 
gains 5 grams in weight, where would this 5 grams of matter come 
from? How much would you expect to fiiiiL that the air had lost in 
weight? 

What is the composition of the air? 

Why are oxygen and nitrogen called elements? 

CHAPTER III. 

Where and in what quantity is oxygen found? 

How can we get oxygen from the air? 

Explain how oxygen is collected when it is set free from the oxide 
of mercury. 

What other ways are there of getting oxygen ? 

What is the appearance of oxygen? Its smell? taste? What hap 
pens to it when it is much cooled down and compressed? 



QUESTIONS AND PBOBLEMS. 245 

How does oxygen behave towards other substances at the ordinary 
temperature? How do you know this? Does oxygen act upon any- 
thing at the ordinary temperature? Give examples. 

Of what importance is oxygen to all animals? What difference is 
there between the action of oxygen at the ordinary temperature and 
at higher temperatures? How did } r ou learn this difference? 

When substances burn in oxygen, is the oxygen used up? What 
becomes of it? Do the substances gain or lose in weight? How 
does the weight of the oxygen used up compare with the gain in 
weight of the substance burned ? 

What does burning in oxygen consist in? 

Is burning in the air the same chemical act as burning in oxygen? 
How can this be proved? Why do substances not burn as actively 
in the air as they do in oxygen? 

What is meant by combustion? 

What are combustible substances? 

What are incombustible substances? 

Is water combustible? Is wood combustible? 

Give an example of a substance which will not burn in the air, but 
which will burn in oxygen. How was this shown? 

What is meant by the kindling temperature? Explain why it is 
that a stick of wood burns gradually and not all at once. 

Explain the connection between the heat and light produced, and 
the combustion of a substance. 

What is meant by the expressions chemical work and chemical 
energy ? 

Do combustible substances possess chemical energy? 

Show how a combustible substance can do work. What are the 
substances called which are found in combustion? Give examples. 

CHAPTER IV. 

Explain what is meant by saving that the elements combine in 
definite weights. 

What is the law of definite proportions? 

How are natural laws discovered? 

What is a natural law? 

In studying the proportions by weight in which the elements com- 
bine with one another, what is observed? 

What are the combining weights of the elements? 

How is a chemical compound expressed by a symbol? 

What does the symbol NaCl mean? What does O stand for? 
What does Fe stand for? 

How does a chemist express what takes place when mercury oxide is 
heated? 

How much mercury is contained in 20 grams of mercury oxide? 

How much oxygen is contained in 30 grams of mercury oxide? 

How much mercury oxide would be necessary to furnish 10 grams 
of oxygen? 

How much mercury oxide would be necessary to furnish 10 grams 
of mercury? 



246 THE ELEMENTS OF CHEMISTRY. - 

Explain what is meant by the law of multiple proportions. Give 
examples illustrating the law. 
What do the symbols S0 2 , C0 2 , and H 2 S0 4 mean? 

CHAPTER Y. 

Where and in what forms is nitrogen found in nature? 

How can we get nitrogen from the air? 

Why do we use phosphorus for the purpose? 

Describe the method of preparing nitrogen. 

How can nitrogen be obtained from the air by the use of copper ? 

What is the color of nitrogen? its taste? its odor? How does it 
differ from oxygen in its conduct towards burning things? Could 
animals live in it? Why? Suppose there were no nitrogen in the 
air, how would our fires differ from the fires in the air? 

What is the difference between a chemical compound and a mechan- 
ical mixture? 

Are nitrogen and oxygen chemically combined or mixed together in 
the air? 

What reasons can you give for your statement? 

CHAPTER VI. 

How can it be shown that water is contained in wood? in meat? 

Is water present in large or small proportion in animal and 
vegetable substances? 

What is meant by water of crystallization? 

What are efflorescent substances? 

What are deliquescent substances? 

Is water an element or a compound? How do you know? 

Describe the experiment in which an electric current is passed 
through water. What does the experiment show? 

CHAPTER VII. 

Where and in what forms is hydrogen met with in nature? 

How is hydrogen obtained? 

What takes place when a piece of sodium is thrown upon water? 

What takes place when steam is passed over heated iron? 

What is water gas, and how is it obtained? 

Which are the common acids? What do they all contain? What 
takes place when they are treated with metallic elements? 

What is the most convenient method for preparing hydrogen? 

Describe the process fully, and show how you can collect the hy- 
drogen. 

What are the properties of hydrogen? 

How is it shown that hydrogen is lighter than air? 

What relation is there between the weights of equal volumes of 
hydrogen and oxygen? 

If the weight of a certain bulk of hydrogen is 1 ounce, what would 
be the weight of the same bulk of oxygen ? 



QUESTIONS AND PBOBLEMS. 247 

What relation is there between the combining weights of hydrogen 
and oxygen and the weights of equal bulks of the two gases? 

When we say that the combining weight of hydrogen is 1 and that 
of oxygen 16, what is meant? What is meant when we say the com- 
bining weight of iron is 56? 

If we should call the combining weight of oxygen 100, what would 
be the combining weight of hydrogen ? 

What change takes place in hydrogen when it is cooled down very 
much and greatly compressed ? 

Does hydrogen combine with cxygen at the ordinary temperature? 
How do you know ? 

What takes place when it is heated in oxygen? 

Does hydrogen support combustion? How can this be shown? 

CHAPTER VIII. 

Is water formed when hydrogen burns? How can this be shown? 
How is it explained ? 

What takes place when a flame or spark is applied to a mixture of 
hydrogen and oxygen? How is this explained? 

How can we show what takes place when a mixture of hydrogen 
and oxygen explodes? What has been shown to take place? How 
does this help us to understand what the composition of water is? 

In what other way can the composition of water be found out? 

Explain exactly how the experiment with copper oxide teaches us 
whit the composition of water is. 

What is meant by reduction? a reducing agent? 

Explain the oxyhydrogen blow -pipe and its uses. 

Explain the lime-light or Drummond light. 

Has water any color? 

Is the water which is found in nature pure? Why is this? 

Why does ice float on water ? 

What is the purest water found in nature? Why? 

What is the character of the water found in mountain streams 
which flow over sand-stone ? Why ? 

What is the character of the water which flows over lime-stone? 

What are mineral springs ? 

How does water become salt? 

What are effervescent waters ? chalybeate waters ? What is sul 
phur water ? 

What are the most common causes of impurities in water? 

What change takes place in river-water which has been contam- 
inated with drainage? 

What precautions should be taken in regard to the position of 
wells? Why? 

How can water be purified ? Describe the process of distillation. 

What kinds of substances cannot be removed from water by distil- 
lation ? 

What is meant by saying that water is the best solvent? 

Why do we use solutions in studying the chemical action of sub- 
stances upon one another? 



248 THE ELEMENTS OF CHEMISTRY. 

What is a solution? 

What is expressed by the symbol H 2 0? 

In what respects do hydrogen and oxygen resemble each other? Id 
what respects do they differ from each other? 

Do hydrogen and oxygen combine readily? Does combination 
take place more readily between those elements which are alike or be- 
tween those which are unlike? 

What change takes place in oxygen when electric sparks are passed 
through it? In what other ways can this change be brought about? 

How can ozone be converted into oxygen? 

When oxygen is changed to ozone, and c zone to oxygen, is there 
any change in weight? 

What is hydrogen dioxide? How is it made? What is its most 
striking property? What is it used for? 

CHAPTER IX. 

What is destructive distillation? 

From what kinds of substances is ammonia given off in destructive 
distillation? 

What is one of the products formed when substances containing 
carbon, hydrogen, and oxygen arc heated? In what experiment 
which you have already performed is this shown? 

Explain why ammonia is formed in gas-works? 

What does the process of decay consist in? 

What becomes of the nitrogen contained in animal substances when 
they decay? 

What connection is there between saltpetre and nitric acid? be- 
tween potassium nitrite and nitrous acid ? 

What is the "ammoniacal liquor" of the- gas-works? What is 
formed when hydrochloric acid is added to this liquor: 

How is ammonia obtained from ammonium chloride? 

Express what takes place in a chemical equation, and explain exactly 
what the equation means. 

[The expression 2NH 4 C1 represents twice the quantity of ammonium 
chloride that is represented by NH 4 C1. So also 2NH 3 represents a 
quantity of ammonia twice as great as is represented by NH 3 ,] 

How much ammonia can be obtained from 50 grams of ammonium 
chloride? 

The combining weight of nitrogen is 14, that of calcium, Ca, is 40, 
and that of chlorine, CI, is 35.5. We have, therefore, these relations ; 

2NH 4 C1 + CaO = 2NH 3 + CaCl 2 + H 2 C 
2(14 + 4 + 35.5) + (40 + 16) = 2(14 + 3) + (40 + 71) + (2 + 16) 



2X53.5 + 56 = 2x17 + 111 + 18 

107~~ + 56 = 34 + 111 + 18 

To determine the quantity of ammonia which can be obtained from 
50 grams of ammonium chloride, we have simply to solve the propor- 
tion 

107 : 34 :: 50 : the weight of ammonia. 



QUESTION'S AND PROBLEMS. 249 

For from 107 parts by weight of ammonium chloride there are 
formed 34 parts by weight of ammonia, and, therefore, as these fig- 
ures are to each other so is 50, the actual weight of ammonium chlo- 
ride used, to the weight of ammonia obtained. 

Describe the process of preparing ammonia from ammonium 
chloride. How is the gas collected? What is the appearance of 
ammonia? What is its odor? What effect does it produce upon 
breathing ? What about its weight ? How is this shown ? Explain 
the use of ammonia for the purpose of making ice. Does ammonia 
burn ? How does water act upon it ? 

What is "spirits of hartshorn " ? 

How is nitric acid formed in nature ? 

How is nitric acid obtained from saltpetre ? Express in an equation 
what takes place. Describe the apparatus used, and give the reasons 
for the arrangement of the apparatus. 

What is the appearance of pure nitric acid? What takes place 
when it is boiled ? when the sun shines directly upon it ? How does 
strong nitric acid act? 

Tyhat is ordinary commercial nitric acid ? Why do substances burn 
in strong nitric acid. Describe some experiments which illustrate 
the power of nitric acid: What does the nitric acid give up to the 
substances upon which it acts ? 

What does nitric acid give up when a metallic element acts upon it? 
Describe what further takes place, and why. 

What is aqua regia, and why has it received this name? 

What compounds does nitrogen form with oxygen ? How does this 
series illustrate the law of multiple proportions ? What is the law of 
multiple proportions ? 

How isnitrous oxide formed ? How is it usually prepared ? Give 
the equation representing the action, and state what it means. 

What are the properties of nitrous oxide ? 

How is nitric oxide made ? What takes place when it is brought in 
contact with the air ? Why is the gas red which first appears in the 
flask used in making nitric oxide ? and why does it afterwards become 
colorless ? Give the equations which represent what takes place when 
nitric acid acts upon copper, and explain what they mean. 

How is nitrogen peroxide formed ? What are its chief properties ? 
For what is it used ? 

CHAPTER X. 

What is meant by saying that oxygen belongs to a family of ele- 
ments? 

In what form does chlorine occur in nature ? in what quantity ? 
What are all the chlorine compounds with which we have to deal 
made from ? 

What two steps are necessary in order to get chlorine out of sodium 
chloride or common salt ? What resemblance is there between the 
process for making hydrochloric acid from common salt and that of 
making nitric acid from sodium nitrate ? What is formed besides 
hydrochloric acid and nitric acid in each case ? 



250 THE ELEMENTS OF CHEMISTRY. 

How is chlorine made in the laboratory? "Why is this method not 
well adapted to the commercial manufacture of chlorine? 

Describe Deacon's process for the manufacture of chlorine. 

Describe Weldon's process for the manufacture of chlorine. 

Describe accurately the method of making chlorine used in the 
laboratory. How is the chlorine collected? What takes place when 
powdered antimony is introduced into chlorine? copper foil? flowers 
and calico? 

What is the appearance of chlorine? its odor? its action upon the 
throat and nose? Is it heavier or lighter than air? What is its 
action upon water? What is bleaching? 

What is disinfection? What is " bleaching-powder" ? What other 
name has it? Why is it valuable as a disinfecting agent? 

Compare the action of hydrogen on oxygen and on chlorine. 
What are the products? What are chlorides? 

What is the simplest way of forming hydrochloric acid? What 
difference is there between the action of a mixture of chlorine and 
hydrogen and a mixture of hydrogen and oxygen? What art is de- 
pendent upon chemical changes caused by light? Describe the 
method of preparing hydrochloric acid. Give the equation express- 
ing the action, and state what it means. 

If 40 grams of common salt are used, how much hydrochloric acid 
and how much sodium sulphate will be obtained? 

How is the hydrochloric acid collected ? What are the properties 
of hydrochloric acid? Give a connected account of all that you 
learned about it in Experiment 65. How can the composition of hy- 
drochloric acid be determined? What is the composition? What 
happens to hydrochloric acid when it is treated with a metallic ele- 
ment like zinc? when treated with an oxide like zinc oxide? When 
treated with substances which give up oxygen readily? 

How are the chief compounds of chlorine, hydrogen, and oxygen 
obtained? What is potassium chloride? potassium hypochlorite? 
potassium chlorate? What takes place when these compounds are 
treated with sulphuric acid ? Express the reactions in equations, and 
show how the reactions resemble one another. Compare the reactions 
with that which takes place when sulphuric acid acts upon sodium or 
potassium nitrate. 

To which of the substances above mentioned is "bleaching-pow- 
der" allied? 

In what way does the series of compounds of chlorine with hydro- 
gen and oxygen illustrate the law of multiple proportions? / 

CHAPTER XI. 

What takes place when an acid and a base are brought together ? 

What are alkalies ? Mention some common acids ; some common 
bases. How can you conveniently tell whether a substance is an acid 
or a base ? 

What did you learn in Experiment 66 ? 

How can you determine what is formed when an acid acts upon a 
base ? What is formed when hydrochloric acid acts upon caustic soda? 



QUESTIONS AND PBOBLEMS. 251 

nitric acid upon caustic soda? sulphuric acid upon caustic soda? hy- 
drochloric acid upon caustic potash? nitric acid upon caustic potash? 
sulphuric acid upon caustic potash? 

What do the experiments performed in regard to the action of acids 
upon bases teach ? 

What is formed when a metallic element acts upon an acid ? 

What is an acid? a base? a salt? 

What is a metal? 

Explain the use of the syllables ic and ous in naming acids ; of 
hypo and per. Give the names and symbols of the compounds of 
chlorine, hydrogen, and oxygen. 

How are bases named? 

Explain how salts are named. What is the name and formula of 
the potassium salt of hypochlorous acid? of perchloric acid? of chloric 
acid? of nitric acid? 

What are the salts of hydrochloric acid called? Why? 

What connection is there between acid properties and oxygen? 



CHAPTER XII. 

What takes place when animal and vegetable substances are heated 
to a high temperature? Why is this? What takes place when they 
are heated in the air? 

Give a familiar example of the process of destructive distillation. 
For what purpose is coal distilled ? wood ? 

What are the principal forms in which carbon occurs in nature? 
Mention some of the most common compounds of carbon. 

What two forms of pure carbon are there? 

Where are diamonds found, and what is the general appearance of 
a diamond when first found? 

How can graphite be made? Compare graphite and diamond, stat 
ing the properties of each. By what other names is graphite known? 

What is amorphous carbon? 

Describe the process by which charcoal is made. 

Compare the properties of charcoal with those of diamond and 
graphite. 

What is coke, and how is it obtained? lampblack? bone-black or 
animal charcoal? 

What are charcoal filters used for? What are bone-black filters 
used for? 

What is the object of charring piles which are exposed to the action 
of air and water? 

What different kinds of coal do we distinguish between? What is 
lignite? peat? 

How was coal formed ? 

What are the chief products of the destructive distillation of coal? 
Are hard or soft coals used in the manufacture of illuminating-gas? 
Why? 

How can it be proved that diamond, graphite, and charcoal consist 
only of the element carbon? What common properties have the dif- 
ferent forms of carbon? 



252 THE ELEMENTS OF CHEMISTRY. 

What is meant by the name allotropism? 

How can we form an idea in regard to the reason why one and the 
same thing can appear in different forms? 

Compare the chemical conduct of carbon with that of the other 
elements thus far considered. 

What is formed when carbon combines directly with oxygen? How 
can this be proved? How can we easily recognize carbon dioxide? 

Explain what takes place when a mixture of charcoal and copper 
oxide is heated ; when a mixture of arsenic and charcoal is heated. 
Is there any resemblance between the action of hydrogen and of 
charcoal on heated copper oxide? 

Why is carbon called a reducing agent? 

What important use is made of charcoal as a reducing agent? 

CHAPTER XIII. 

What are hydrocarbons? Are these easily formed in the labora- 
tory? Under what circumstances are they easily and abundantly 
formed? 

What is petroleum? Why must it be refined before it is fit for use 
in lamps? How is it refined? What is the product called? 

What are some of the light products obtained when petroleum is 
refined? What is paraffin ? 

Give the names and symbols of the four simplest hydrocarbons 
coutained in petroleum. 

What is meant by homology, and an homologous series? 

Give the names and symbols of the first three members of the ethy 
lene series. 

Give the names and symbols of the first two members of the acety- 
lene series. 

Give the names of the first three members of the benzene series. 

Where is marsh-gas found, and under what circumstances is it 
formed? What are the final products of the oxidation of vegetable 
matter? What is the chief product of the reduction of vegetable 
matter? 

Of what importance is the occurrence of marsh-gas in coal-mines? 

How is marsh-gas made in the laboratory? 

What are the properties of marsh-gas? 

How is ethylene obtained, and what are its properties? What other 
name has it? 

How is acetylene formed, and what are its properties? 

Describe in brief the method of making coal-gas. 

What is coal-tar? Mention some of the products obtained from it. 

What is the principal compound of carbon and oxygen? 

Where and. in what forms is carbon dioxide found? 

What processes which are constantly taking place give rise tc the 
formation of carbon dioxide ? 

How is carbon dioxide most easily made ? Describe the process 
accurately. Express the action by means of a chemical equation, and 
state what it means. 

What are the properties of carbon dioxide? 



QUESTIONS AND PROBLEMS. 253 

Why does not carbon dioxide burn ? 

What is meant by the statement, " Carbon can do chemical work" ? 
What resemblance is there between a piece of carbon and an ele- 
vated body of water ? 

What is soda-water, and how is it made ? 

What connection is there between the breathing process and carbon 
dioxide ? Is carbon dioxide poisonous ? 

Why is the air in badly ventilated rooms bad to breathe V 

Why is carbon dioxide apt to be found in old wells ? How can it 
be detected if present in large quantity ? 

What is choke-damp, and what does the name come from ? 

Of what importance to plants is the carbon dioxide in the air ? Of 
what importance is it to animals ? What resemblance is there between 
the food of animals and the fuel burned in stoves ? 

How does the carbon of animals and plants get back into the air 
again ? 

In what way is all life directly dependent upon the sun ? 

How are carbonates formed ? What is the composition of sodium 
carbonate ? of potassium carbonate ? What, then, is the composition 
of carbonic acid ? What takes place when carbonic acid is set free 
from carbonates ? 

What takes place when carbon dioxide acts upon potassium hy- 
droxide ? upon calcium hydroxide ? Give the equations representing 
the action, and name the products. 

What takes place when carbon dioxide is passed into lime-water 
until no further action is observed ? What change occurs when the 
solution thus obtained is boiled ? 

What are hard waters ? How are they formed ? Why do we make 
the distinction between temporary and permanent hardness ? What 
objection is there to hard waters ? 

How is carbon monoxide formed ? Explain its formation in open 
grate fires. What is the blue flame at the top of a coal fire due to ? 

Why is the use of water-gas sometimes objected to ? 

How is carbon monoxide made ? 

What are its properties ? 

What danger is there connected with the use of coal stoves ? Why 
is smouldering charcoal a dangerous thing to have in a room ? 

Why is carbon monoxide a good reducing agent ? 

Of what importance is it in the reduction of iron from its ores ? 

What is a flame ? What is the difference between a candle and a 
lamp ? 

How can it be shown that when a burning gas is cooled down it is 
extinguished ? 

Explain the construction of the miner's safety-lamp, and the reason 
for its use. 

Why do some flames give light and others not ? 

How are cyanides formed ? What is yellow prussiate of potash, 
and how is it made ? What is potassium cyanide ? How is cyanogen 
made ? What are its properties ? 

Where is prussic acid found ? How is it made ? What are its 
properties ? 



254 THE ELEMENTS OF CHEMISTRY. 

CHAPTER XIV. 

What are the two principal laws governing chemical action ? 

Do we know why substances combine according to the laws of defi 
nite and multiple proportions ? 

What is an hypothesis ? a theory ? 

What theory has been suggested to explain the laws of definite and 
multiple proportions ? 

Show how this theory accounts for the facts ? 

What is meant by the atomic weights ? 

What is meant by the expression molecule ? 

What are the symbols of the elements intended to represent ? the 
symbols of compounds ? 

Explain in full what the symbols HN0 3 , H 2 S0 4 , 1STH 3 , CH 4 , and 
CO 2 are intended to represent. What relation is there between the 
weight of a molecule and the weights of the atoms of which it is made 
up ? 

What is Avogadro's law. 

How does Avogadro's law help us to determine the relative weights 
of the molecules of gaseous substances ? 

How are the atomic weights determined from the molecular 
weights ? 

What difference is there between chlorine, oxygen, nitrogen, and 
carbon as shown by the symbols of their compounds with hydrogen ? 
What is meant by the valence of an element ? 

What is meant by a univalent element ? a bivalent element ? a 
trivalent element ? a quadrivalent element ? Barium forms the com- 
pound BaCl 2 ; what is the valence of barium ? Sodium forms the 
compound NaCI ; what is the valence of sodium ? 

In the formation of potassium nitrate from nitric acid, how is the 
valence of potassium shown ? When a bivalent element like calcium 
forms a salt with nitric acid, how does the displacement of hydrogen 
take place ? Calcium is bivalent. What is the symbol of its salt 
with sulphric acid ? Explain this. What is the symbol of the sodium 
salt of sulphuric acid ? What does this show with regard to the 
valence of sodium ? 

If magnesium, Mg, is bivalent, what is the symbol of its sulphate ? 
of its nitrate ? of its chloride ? What is the basis for the distinction 
between acid-forming and base-forming elements ? Give examples of 
the two classes. What are these classes sometimes called ? 

What is meant when we speak of a family of elements ? 

What are the families of acid-forming elements ? 

CHAPTER XV. 

Name the members of the chlorine family. 

Why is fluorine included in this family ? 

In what forms does bromine occur in nature ? 

How is bromine obtained from sodium bromide ? Give the equa- 
tions representing the steps which must be taken, and explain what is 
meant by them. 



QUESTIONS AND PBOBLEMS. 255 

What are the properties of bromine ? What are the chief d fferences 
between bromine and chlorine ? 

What is hydrobromic acid, and how is it formed ? What difference 
is there in the conduct of common salt and of sodium bromide to- 
wards sulphuric acid ? How is this explained ? 

What compounds does bromine form with hydrogen and oxygen ? 

In what forms does iodine occur in nature ? How is it obtained in 
Scotland and France ? What is kelp ? 

How is iodine obtained from sodium iodide ? Give the equations 
representing the action, and explain what they mean. 

What are the properties of iodine ? Compare chlorine, bromine, 
and iodine, stating the points of resemblance and difference. 

How can you easily tell whether a substance is an iodide or not ? 

How is hydriodic acid obtained? How does it differ from hydro- 
chloric and hydrobromic acids? What takes place when potassium 
iodide is treated with sulphuric acid? 

In what forms does fluorine principally occur in nature? 

How is hydrofluoric acid made, and what are its properties? Give 
the equation representing the action of sulphuric acid on fluor-spar? 
What use is made of hydrofluoric acid? Can the substance be kept 
in glass bottles? 

What analogy is there between chlorine, bromine, and iodine, as far 
as the compounds which they form are concerned ? 

What relation is there between the atomic weights of chlorine, bro- 
mine, and iodine? 

CHAPTER XVI. 

Name the members of the sulphur family. Why has sulphur been 
known for a long time? Where is it found in nature? What is the 
chief source of the sulphur of commerce? Name some of the princi- 
pal compounds in which sulphur occurs in nature? 

Describe the process by which sulphur is extracted from its ores. 

How is crude brimstone refined ? What is the difference between 
"flowers of sulphur" and "stick sulphur"? Give the properties of 
sulphur. What changes does it undergo when it is distilled? 

What two forms can sulphur be obtained in? How can it be thus 
obtained? How do the two forms differ from each other? 

How does sulphur act when heated in the air? 

What are sulphides? How are they formed? 

Can sulphur and hydrogen be made to combine directly? What 
is formed? Where is' this compound found in nature? Under what 
conditions is it formed? 

How is hydrogen sulphide made in the laboratory? Explain what 
takes place when sulphuric acid is used ; when hydrochloric acid is 
used. How is the substance collected? What are its properties? 
How does it behave towards water? towards metals? What takes 
place when it is passed over heated iron? Is there any resemblance 
between this action and that which takes place wiien steam is passed 
over heated iron? Express both acts by chemical equations. 

What takes place when hydrogen sulphide is passed through solu- 
tions containing metals in the form of soluble salts? 



256 THE ELEMENTS OF C&EMlSTBT. 

How can hydrogen sulphide be used for the purpose of learning 
what things are made of? What is formed when sulphur is burned 
in the air? What is formed when sulphur dioxide takes up more 
oxygen? What is the product of the action of sulphur trioxide on 
water? What relation is there between sulphurous acid and sulphuric 
acid? 

Where is sulphur dioxide found in nature? How is it made in the 
laboratory? Explain the reactions, giving the equations. 

What are the properties of sulphur dioxide? What uses are made 
of sulphur dioxide? 

How are sulphites made? What is the composition of sodium sul- 
phite? What takes place when sodium sulphite is treated with sul- 
phuric acid? with hydrochloric acid? Compare these reactions with 
those which take place when sodium carbonate, Na 2 C0 3 , is treated 
with sulphuric acid and with hydrochloric acid. 

Mention some salts of sulphuric acid which are found in nature. 
How is sulphuric acid made? Explain the action of nitric oxide in 
oxidizing sulphurous acid. 

Describe the manufacture of sulphuric acid. Describe the arrange- 
ment of a leaden chamber. 

What is oil of vitriol, and how is it obtained? How does sulphuric 
acid act upon sodium chloride? upon potassium nitrate? 

How does sulphuric acid act towards water? How does it act upon 
organic substances which contain hydrogen and oxygen? What 
change does it produce in wood? Explain the change. 

Of what importance is sulphuric acid in the arts? 

What marked difference in conduct is there between sulphuric acid 
and hydrochloric and nitric acids? 

What is a monobasic acid? a dibasic acid? 

Define acid, normal, and neutral salts. 

What is carbon disulphide? How is it made, and what are its prop- 
erties? 

Why are selenium and tellurium included in the sulphur family? 

What relation is there between the atomic weights of sulphur, sele- 
nium, and tellurium ? Has any similar relation been noticed in the 
case of other elements? 

CHAPTER XVII. 

How does phosphorus occur in nature? What is a phosphate? 

How is phosphorus made? 

What are the properties of phosphorus? 

Explain what takes place when phosphorus and iodine are brought 
in contact with each other. 

What is red phosphorus? How is it made from ordinary phos- 
phorus? Compare the two varieties of phosphorus. How is ordinary 
phosphorus made from red phosphorus? 

Describe the changes which take place when phosphorus is burned 
in the air or in oxygen, and the product dissolved in water. 

How is ordinary phosphoric acid made? What salts does it form 



QtmsTiows Ajsrn problems. 257 

with sodium? What is normal calcium phosphate? Why is phos- 
phoric acid called a tribasic acid? 

In what compounds is the element arsenic found in nature? What 
are its properties? 

What compound does arsenic form with hydrogen ? What com- 
pound of nitrogen is it analogous to? How is it formed? Explain 
all that takes place in Experiment 98. 

What are the properties of arsine? What is Marsh's test, and for 
what is it used? 

What is the substance which is usually called arsenic? How is it 
obtained from the element arsenic, and from the compounds of ar- 
senic with metals? What are its properties? 

Explain what takes place when arsenic trioxide and charcoal are 
mixed together and the mixture heated. In what form does antimony 
chiefly occur in nature? What are its general properties? 

Compare stibine and arsine. 

In what forms does boron occur in nature? How is it prepared? 
What are its properties? 

What is borax, and from what acid is it derived? 

Mention some of the principal compounds of silicon which occur in 
nature. Is it a rare or common element? What other element does 
it resemble in some respects? 

Does silicon occur in nature in the uncombined state? How is the 
element obiained? 

Mention some of the varieties of silicic acid, aiid point out the rela- 
tion which exists between them. 

Mention some of the principal varieties of silicon dioxide which oc- 
cur in nature. 

What important manufactured product contains silicon? 

CHAPTER XVIII. 

What is meant by the name base-forming elements ? What name 
is given to the elements which are not base-forming elements ? How 
does the number of base-forming elements compare with the number 
of acid-forming elements ? 

What is meant by metallic properties ? 

What are the chief classes of metal derivatives ? 

What are minerals ? 

What is meant by the term metallurgy ? 

CHAPTER XIX. 

What are the alkalies, and why are they so called ? 

In what form is potassium found in nature ? Of what importance 
is the element potassium to plants ? Where does the potassium 
which the plants use come from ? What is left when wood is burned ? 
Suppose you wanted potassium sulphate, and had only wood ashes 
and sulphuric acid, how could you get it ? 

In what other forms besides those mentioned does potassium occur 
in nature \ 

17 



258 THE ELEMENTS OF CHEMISTRY. 

How is potassium obtained from its compounds ? What are its 
properties ? Explain what takes place when potassium acts upon 
water. 

How is potassium iodide made ? Explain the reactions. What 
takes place when potassium iodide is treated with sulphuric acid ? 
What is potassium iodide used for ? 

How is potassium hydroxide formed? What is its common name? 
Explain the reaction which is used in making potassium hydroxide. 
What are the properties of the hydroxide ? What change does it 
undergo when exposed to the air ? Where is saltpetre found, and 
under what conditions is it formed ? 

Describe the saltpetre plantations. How is saltpetre used in mak- 
ing sulphuric acid ? How is it used in making nitric acid ? 

Give an account of the manufacture of gunpowder, and explain its 
use as an explosive. 

In what forms is sodium found in nature ? What are its proper- 
ties ? How does it differ from potassium ? 

What is meant by saying that sodium is a good reducing agent ? 
What is sodium amalgam, and for what is it used ? 

Where and in what quantities is sodium chloride found ? 

How is salt obtained from natural sources ? 

What are the properties of sodium chloride ? 

What are the chief uses of salt ? 

What is caustic soda, and how is it obtained ? 

Where is sodium nitrate found ? Why can it not be used in mak- 
ing gunpowder ? How can potassium nitrate be made from it ? 

What is the common name of sodium sulphate ? In what impor- 
tant manufacturing process is it obtained ? What percentage of 
water of crystallization does it contain ? What change takes place in 
it when it is left in contact with the air ? Is it deliquescent or efflor- 
escent ? 

Of what importance is sodium carbonate ? From what source was 
it formerly obtained ? 

How did Leblanc come to devise a method for making sodium car- 
bonate ? 

Describe Leblanc's process. 

Describe the Solvay process. 

What percentage of water of crystallization does sodium carbonate 
contain ? 

What relation does bicarbonate of soda bear to sodium carbonate ? 
How is it made ? Explain its use in baking-powders. 

What is the substance which is commonly called phosphate of soda t 

What is the composition of borax ? Where is it found in nature ? 
What change takes place in borax when it is heated ? Explain the 
use of borax in soldering. What is meant by saying that borax is an 
antiseptic ? 

What is water-glass, and how is it made ? What is it used for ? 

What action takes place when ammonia is brought together with 
acids ? What are the products when hydrochloric, nitric, acd sul- 
phuric acids are treated with ammonia ? Why are these substances 



QUESTIONS AND PROBLEMS. 259 

included among the derivatives of the potassium family ? "What is 
the difference between ammonia and ammonium ? 

What is sal ammoniac, and how is it chiefly obtained ? Give the 
equations expressing the reactions which take place when sal ammo- 
niac is treated with caustic soda and with quick- lime. 

How is ammonium sulphide made, and what is its composition ? 

What relation exists between the atomic weights of the alkali 
metals ? 

What are flame reactions, and how are they used for the purpose of 
detecting substances ? 

How can potassium and sodium be detected when both are pres 
ent ? 

What is a spectrum ? How can the spectrum of a light be used for 
telling what substances are in the flame ? 

What are the principal parts of the spectroscope ? Of what ser- 
vice has it been to chemistry ? 



CHAPTER XX. 

Mention some of the chief compounds of calcium found in nature. 

Of what interest is calcium chloride ? How is it made ? 

What is ]ime ? How is it made ? Explain a lime-kiln. Explain 
the use of lime in making the lime-light. What change takes place 
when lime is left exposed to the air ? What change takes place in it 
when it is treated with water ? What is lime water ? What changes 
are produced in lime-water by passing carbon dioxide into it V 

What is bleaching-powder, and how is it made ? Of what value is 
bleaching-powder ? Under what conditions does it give up its chlo- 
rine ? 

Mention some of the principal varieties of calcium carbonate which 
are founl in nature. What are stalagmites and stalactites ? 

What is gypsum ? Explain the use of plaster-of -Paris. 

Explain the difference between permanent and temporary hardness 
of water. 

How can temporary hardness be remedied ? How can permanent 
hardness be remedied ? Explain the action in each case. 

What application is made of gypsum ? 

What forms of calcium phosphate are found in nature ? What is 
meant by the name normal calcium phosphate ? 

Of what importance is calcium phosphate to plants ? What objec- 
tion is there to the use of normal calcium phosphate as a fertilizer ? 
What is superphosphate of lime, how is it made, and what is it used 
for ? 

How is mortar made ? Why do freshly-plastered rooms remain 
moist so long ? How can the process of drying be hastened ? 

What is common glass ? What is the difference between sodium 
glass and potassium glass ? What is flint-glass, and for what is it used? 

How are colored glasses made ? 

Explain how barium dioxide is used for extracting oxygen from, 
the air. How is it used in making hydrogen dioxide ? 



260 THE ELEMENTS OF CHEMISTRY. 

What flame reactions do calcium compounds give ? strontium com 
pounds ? barium compounds? 

What relation exists between the atomic weights of calcium, stron- 
tium, and barium ? 

CHAPTER XXI. 

Mention the chief compounds of magnesium which are found in 
nature. 

How is magnesium prepared ? What are its most striking proper 
ties ? 

What is magnesia? What change does water effect when brought 
in contact with magnesia? 

Mention the chief forms in which zinc is found in nature, 

How is zinc got out of its ores? 

What are the most striking properties of zinc? 

What is galvanized iron? brass? German silver? 

Explain what takes place when zinc is heated to a high tempera- 
ture in the air. 

What is zinc- white? What advantage has it over lead- white? 

What is white vitriol? In what experiments which you have per 
formed has it been obtained? How is it made on the large scale ? 
What are the final products of roasting zinc sulphide? 

Where and in what form does copper chiefly occur in nature ? 
What is the substance known as copper pyrites? 

What takes place when an oxide of copper is heated with charcoal? 
Explain the reaction. What are the most striking properties of cop 
per? What takes place when it is heated with nitric acid? with sul- 
phuric acid? 

Explain the process of copper-plating. 

What are alloys? What is brass? bell metal? bronze? 

What is the difference ia composition between cuprous and cupric 
compounds? Give examples. 

What is the composition of cuprous oxide, and what is the name of 
that variety of it which occurs in nature? 

How is copper oxide made? Explain what takes place when a so- 
lution of caustic soda is added to a cold solution of copper sulphate 
which is afterwards boiled. 

; What is the most common salt of copper? What effect does heat- 
J ing produce upon the substance? 

In what forms does mercury occur in nature? How is it obtained 
from its chief compound? Why are mercury thermometers of no 
value in arctic regions? 

What are the alloys of mercury called? Why are the zinc plates in 
galvanic batteries amalgamated? How is mercuric oxide formed? 
For what has it been used in experiments which you have performed? 

What is calomel, and how is it obtained? For what is it used? 

What is corrosive sublimate, and how is it manufactured? What 
objection would there be to having a little corrosive sublimate mixed 
with the calomel which is used in medicine? 

In what forms does silver occur in nature? Explain how silver is 



QUESTION'S AND PROBLEMS. 261 

extracted from galenite: (1) by Pattison's process; (2) by the amal- 
gamation process. 

What action do air and water have upon silver? Why do silver 
coins, etc., carried in the pockets become dark-colored? Why do 
silver spoons used in eating eggs become tarnished (see near the bot- 
tom of page 142)? 

Why is not pure silver used in making coins? What is used? 

How is silver-plating accomplished? How are mirrors made? 

How is silver nitrate made? Why is this salt used in making in- 
delible inks? How can stains made by silver nitrate be removed? 

Explain all the chemical processes made use of in Experiment 117, 
for the purpose of making pure silver nitrate from a silver coin. 
Whit change takes place in silver chloride when it is exposed to the 
light? in silver bromide? in the iodide? 

What example have we already had to deal with which showed 
that light can produce chemical changes? 

Explain in brief the chemical changes upon which the art of pho- 
tography is based. 

CHAPTER XXII. 

Mention some of the principal compounds of aluminium which 
occur in nature. 

How is aluminium made? 

What are the most important properties of aluminium? How does 
its weight compare with that of the metals in common use? What 
advantage does it possess over iron? 

What are the forms of aluminium oxide found in nature? How 
can the oxide be made in the laboratory? 

What is ordinary alum? What are the alums? Give examples. 
What relation do they bear to sulphuric acid? 

What uses are made of alum? 

What is the principal silicate containing aluminium? How does 
the element potassium get into the soil? Where does clay come from? 
Would you expect to find loose soil mostly on the tops of mountains 
or in valleys? Why? What is kaoline? 

What is porcelain? Explain the process of glazing. 

What is ultramarine, and how is it made? 

What is aluminium bronze, and how is it made? 

Mention the chief compounds of iron which are found in nature. 
Where is iron found in the uncombined state? 

Explain the process of extracting iron from its ores. What is a flux? 
What is slag? 

What is pig-iron? cast-iron? wrought-iron ? How is cast-iron con- 
verted into wr ought-iron? What is steel? How is steel tempered ? 
How is steel made? 

What are the properties of pure iron? Explain the change which 
iron undergoes in moist air. What is given off when iron is dissolved 
in hydrochloric acid? 

What is the difference in composition between the ferrous and 
ferric compounds? Give the formulas of ferrous and ferric sulphates, 



262 THE ELEMENTS OF CHEMISTRY. 

ferrous and ferric oxides. How could we decide whether the formula 
FeCU or Fe 2 Cl 4 is the correct one for ferrous chloride? 

How are ferrous compounds converted into ferric compounds? 
Why is the change hastened by adding nitric acid? 

How is ferrous chloride made? Explain the changes which take 
place when caustic soda is added to its solution, and the mixture is 
allowed to stand in contact with the air; when the solution is boiled 
aud a few drops of nitric acid added. How can ferric chloride be 
converted into ferrous chloride? 

What is copperas, and what other names has it? What is it used 
for? What are some of the different kinds of ink? 

Compare the formula of iron-alum with that of ordinary alum. 

What is the principal variety of ferric oxide? What is rouge, and 
how is it made? What is the composition of loadstone? Under what 
circumstances is this oxide formed? 

How is ferrous sulphide made? For what has it been used in ex- 
periments already performed? 

What is iron pyrites? What changes take place in it when it is 
heated in an open vessel ? 

In what forms is nickel found in nature? Why is nickel used for 
plating other metals and for making coins? 

In what forms is cobalt found in nature? What are cobalt com- 
pounds principally used for? What is smalt? What is cobalt ultra- 
marine? 

CHAPTER XXIII. 1/ 

What is the chief compound of manganese found in nature? 
What other compounds with oxygen does manganese form? 

What is the chief natural compound of chromium? 

What is potassium chromate, and how is it made? What is potas 
sium dichromate, and how is it made? Explain the relation which 
exists between potassium chromate and potassium dichromate. How 
is potassium dichromate converted into potassium chromate? 

What takes place when potassium chromate or dichromate is 
treated with hydrochloric acid? 

What is chrome -yellow? How is it made? 

What is chrome-alum? Explain its relation to the other alunu 
which have been mentioned. 

In what form does the element uranium occur in nature? 

In what form does bismuth occur in nature, and how is it obtained 
from its ores? 

What is fusible metal? 

What is formed when bismuth is burned in the air? 

What is the chief salt of bismuth ? 



CHAPTER XXIV. 



1/ 



In what compounds does lead occur in nature? 
How is lead extracted from its ores? 

What are the chief properties of lead? Explain the formation of 
the " Arbor Saturni." 



QUESTION'S AND PROBLEMS. 263 

What objection is tbere to the use of lead pipes for conveying 
water for drinking purposes? How can lead be detected in water? 
What did you learn in Experiment 125 in regard to the action of 
water on lead? 

What compounds does lead form with oxygen? What takes place 
when lead is heated in the air? 

What advantage is taken of this fact in separating lead and silver? 

What is red lead? What other name has it? What change does 
nitric acid effect in it? 

What is lead peroxide? What is formed when hydrochloric acid 
acts upon lead peroxide? 

How could you get the sulphate, chloride, and chromate of lead? 

What is white lead? Why does white lead turn black and zinc- 
white not? 

In what form does tin chiefly occur in nature? How is the metal 
obtained from the ore? 

What is tin-foil? What effect does air have on tin at the ordinary 
temperatures? What effect does nitric acid produce on tin? 

What is tin-ware? What danger is there in the use of inferior tin- 
ware? What are pins made of? 

What is solder? britannia? bronze? bell-metal? Explain the pro- 
cess of soldering. What objection is there to the use of solder in 
closing tin cans containing things which are to be eaten? 

What is the difference in composition between stannous and stannic 
compounds? 

What is tin salt? What is it used for? What is mosaic gold? 

In what form does platinum occur in nature? Where' is it chiefly 
found? How is it obtained from its ores? 

What are the most striking properties of platinum? 

For what purposes is platinum used? 

In what form does gold occur in nature? 

How is it usually extracted from its ores? 

What are its most striking properties? 

Why is not pure gold used in making gold ware and coins? What 
is 20-carat gold? What is the composition of the standard gold coin 
of the United States? 

CHAPTER XXV. 

What was the first meaning of the name organic chemistry? inor- 
ganic chemistry? What does organic chemistry mean now? 

Mention some of the principal forms in which carbon occurs in 
nature? 

What takes place when coal is distilled ? 

What takes place when wood is distilled ? 

What takes place when bones are distilled? 

What is meant in general by fermentation? What is the best 
known example of fermentation? 

Mention some of the principal classes of compounds of carbon. 

How is methyl alcohol formed? What other name has it? What 
are its chief properties? 



264 THE ELEMENTS OF CHEMISTRY. 

How is ordinary alcohol madel Explain what took place in Ex- 
periment 128. 

What change takes place in sugar when it undergoes fermentation? 
What causes the change in the sugar? Why do fruit-juices lose their 
sweetness whon exposed to the air? 

Mention some other kinds of fermentation besides alcoholic fer- 
mentation. 

How is alcohol obtained from fermented liquids? What is fusel- 
oil? 

What are the chief properties of ethyl alcohol? 

What are the chief uses of alcohol ? 

What is glycerin? How is it obtained? What are its chief proper 
ties? 

What is formic acid, and where is it found in nature? What are its 
chief properties? 

What is acetic acid? What is "mother of vinegar "? How is 
acetic acid made? Whence come the names pyroligneous acid and 
wood- vinegar? 

What are the chief properties of acetic acid? For what purposes 
is it used? What are the principal salts of acetic acid? 

What are the fatty acids? Mention some of the principal fatty 
acids. What is such a series as that of the fatty acids called ? 

Of what interest is butyric acid? palmitic acid? stearic acid? 

What are soaps? How are they made? How does soap act in 
washing? 

What happens when soap is added to a hard water? Why do the 
hands feel sticky when we attempt to wash them in hard water? 

What connection is there between soap and civilization? How is 
soft-soap made? What connection is there between the manufacture 
of sulphuric acid and sodium carbonate and that of soap? What is 
the composition of oxalic acid ? Where and in what form is it found 
in nature? How is it manufactured ? For what is it used? What is 
the composition of lactic acid? How n it formed? 

Where is malic acid found in nature? Where is tartaric acid 
found in nature? 

What is "cream of tartar," and under what circumstances is it 
formed? 

Where is citric acid found in nature? How is it prepared? 

What is ordinary ether? How is it made? 

What is meant by the word anaesthetic? 

What is the action of an alcohol upon an acid? What is the 
product called? What class of substances do the alcohols act like? 
Compare the action of nitric acid upon alcohol and upon caustic 
potash. 

What is meant by saponification? 

What are fats? Explain what takes place when fats are treated 
with an alkali. 

What does butter consist of? oleo-margarin? 

What connection is there between the flavors of fruits and ethereal 
salts? 

What Is nitro-glycerin? To what class of substances does it be- 



QUESTIONS AND PBOBLEMS. 265 

long? What is dynamite? What relations exist between the hydro- 
carbons of the marsh-gas series and the simplest nlcohols and acids? 

What is an alcohol ? 

What similarity is there between aluminium hydroxide and glycer 
in? 

What is meant by the expression radical or residue ? 

What common acid are the organic acids related to? 



CHAPTER XXYI. 

What are the carbohydrates? 

Where is dextrose found ? What other names has it? 

How is dextrose formed? What relation exists between it and cane 
sugar? between it and starch? 

Describe the process used in the manufacture of glucose. 

What are the chief properties of glucose ? How does it differ from 
cane-sugar? How can alcohol be obtained from it? How lactic 
acid? 

What is ievulose? What relation exists between it and cane-sugar 7 

Where is cane-sugar found in nature? 

Describe the process of sugar- refining. 

What is molasses? What are the chief properties of sugar? What 
is caramel? invert-sugar? What is the action of yeast upon cane- 
sugar? What is sugar of milk? What are the constituents of cow's 
milk? How is cheese made? What is it? How is sugar of milk 
obtained from milk? What does the process of souring of milk con- 
sist in ? 

Of what importance is cellulose in the vegetable kingdom? What 
takes place when cellulose is treated with concentrated sulphuric aci'l 
and boiled? What is gun-cotton? collodion? What is collodion used 
for? What is celluloid? What is paper? Describe the process of 
paper-making. 

In what forms is starch found in nature? Describe the manufacture 
of starch. What is starch-paste? What change is effected in starch 
by dilute acids and ferments? 

What are the chief constituents of flour? 

What causes bread ' rise? 

WhLt is meant by tl name " aromatic compounds "? 

What is nitro-benzene, and how is it made? 

How is aniline made? What is magenta? What are the aniline 
dyes? 

What is carbolic acid? 

What is the oil of bitter almonds? Where is it found in nature? 
What is it used for ? 

What is the source of benzoic acid? What are balsams? Give 
some examples. 

Where is gallic acid found? How is i+ prepared? 

Where does tannic acid occur? For what is it used? 

What does the process of tanning consist in? In what form antf 
where does indigo occur in nature? 



266 



THE ELEMENTS OF CHE MIST BY. 



What is naphthalene? anthracene? What is the chief use of 
anthracene? 

What is alizarin? How is it made? 

What are the giucosides? What examples have already been men- 
tioned? Of what importance is myronic acid? 

What are the alkaloids? What simple inorganic compound do 
they resemble? What is the source of quinine? cocaine? nicotine? 
morphine and narcotine? 



INDEX. 



Acetylene, 108, 109 
Acid, acetic, 221 

benzoic, 239 

boric, 158 

bromic, 134 

butyric, 222 

carbolic, 238 

carbonic, 116 

chloric, 86, 87 

chlorous, 86, 87 

chromic, 206 

citric, 225 

formic, 221 

gallic, 239 

hydriodic, 135 

hydrobromic, 133 

hydrochloric, 82 

hydrocyanic, 122 

hydrofluoric, 135 

hypobromous, 134 

hypochlorous, 86 

lactic, 225 

malic, 225 

metaphosphoric, 155 

metastannic, 212 

myronic, 241 

nitric, 69 

nitrous, 67 

oleic, 227 

orthophosphoric, 155 

oxalic, 224 

palmitic, 222 

perchloric, 87 

phosphoric, 155 

propionic, 222 

prussic, 122 

pyroligneous, 221 

silicic, 159 

stearic, 282 



Acid, sulphuric, 147 

sulphurous, 147 

tannic, 239 

tartaric, 225 

tetraboric, 158 
Acids, 88, 91, 221, 229 

characteristics, 91 

dibasic, 151 

fatty, 222 

monobasic, 151 

names of, 92 

tribasic, 155 
Acid-forming elements, 130 
Agate, 160 
Air, 20 
Alcohol, ethyl, 218 

methyl, 218 
Alcohols, 218, 228 
Alizarin, 241 
Alkalies, 88 
Alkaloids, 241 
Allotropism, 101 
Alloys, 188 
Allylene, 108 
Alum, 197 
Aluminium, 196 

bronze, 199 

hydroxide, 197 

oxide, 197 

silicates, 198 
Alums, 197 

Amalgamation process, 192 
Amalgams, 190 
Amethyst, 160 
Amygdann, 239 
Ammonia; 67 

formation, 65 

in air, 20 

in gas liquor, 67 



268 



INDEX. 



Ammonium, 174 

chloride, 174 

salts, 174 

sulphide, 175 
Analysis, 144 
Aniline, 238 

dyes, 283 
Anthracene, 240 
Anthracite coal, 100 
Antimony, 158 
Apatite, 153 
Aqua regia, 73 
Aromatic compounds, 237 
Arsenic, 155 

oxide, 157 
Arsine, 156 
Asbestos, 185 
Atomic theory, 125 

weights, 126 

determination of, 127 
Atoms, 125 
Avogadro's law, 126 

Baking-powders, 173 
Balsams, 239 
Barium, 183 

dioxide, 184 

oxide, 183 

sulphate, 139 
Bases, 88, 91 

names of, 93 
Bell metal, 188 
Benzene, 108 
Benzine, 107 
Benzoic aldehyde, 238 
Bessemer process, 201 
Bicarbonate of s^da, 173 
Bismuth, 208 

nitrate, 208 

oxide, 208 
Bituminous coal, 100 
Blast furnace, 200 
Bleaching, 80 

powder, 87, 180 
Blow-pipe, compound, 58 

oxyhydrogen, 58 
Bone oil, 217 
Borax, 158, 173 
Boron, 158 

crystallized, 158 

oxide, 158 



Brass, 186, 188 
Bread-making, 237 
Breathing, 26, 113 
Britannia, 212 
Bromine, 132 
Burning in air, 17, 28 

in oxygen, 27 
Butane, 107 
Butylene, 108 

Cadmium, 185 
Caesium, 177 
Calamine, 186 
Calcium, 178 

carbonate, 180 

chloride, 178 

fluoride, 178 

hydroxide, 179 

hypochlorite, 180 

oxide, 178 

phosphate, 182 

sulphate, 181 
Calcspar, 130 
Calomel, 190 
Cane-sugar, 232 
Caramel, 233 
Carbohydrates, 231 
Carbon, 95 

as food for plants, 115 

dioxide, 110 

disulphide, 151 

in the air, 114 

monoxide, 117 
Carbonates, 116 
Carbonic acid, 116 
Carnelian, 160 
Casein, 234 
Cast-iron, 200 
Celluloid, 235 
Cellulose, 234 
Cementation, 201 
Chalk, 180 
Charcoal, 97 

animal, 98 

reduction by, 104 

wcod, 98 
Chemical energy, 30 

work, 30 
Chemistry, 2 
Chloride of lime, 180 
Chlorine, 77 



INDEX. 



269 



Chlorine acids, 86, 87 

bleaching by, 80 

comparison with bromine 
and iodine, 136 

oxides, 87 
Chromates, 206 
Chrome alum, 207 

yellow, 20r 
Chromic iron, 206 
Chromium, 206 
Cinnabar, 190 
Clay, 159, 196, 198 
Coal, 100 
Coal-tar, 110, 217 
Cobalt, 205 
Cocaine, 242 
Coke, 98 
Collodion, 235 
Combination, chemical, 11 
Combining weights, 33 
Combustion, 28 
Compounds, chemical, 9 
Copper, 187 

alloys, 188 

chlorides, 189 

oxides, 189 

plating, 188 

pyrites, 139, 187 

sulphate. 190 
Corrosive sublimate, 191 
Corundum, 197 
Cream of tartar, 173 
Cryolite, 135 
Cupellation, 192 
Cupric compounds, 189 
Cuprous compounds, 189 
Cyanogen, 122 

Deacon's process, 78 
Decomposition, 11 
Definite proportions, law of, 31 
Deliquescent substances, 42 
Dextrose, 231 
Diamond, 96 
Disinfection, 81 
Distillation, 61 

destructive, 66, 95, 217 

of bones, 217 

of coal, 100, 217 

of wood, 217 
Dolomite, 185 



Dynamite, 228 

Earthenware, 198 
Efflorescent substances, 42 
Elements, 9, 10 

classification, 129 

names, 14 

symbols, 14 
Emery, 197 
Epsom salt, 185 
Essence of apples, 227 

pineapples, 227 
Etching, 136 
Ethane, 107 
Ether, 225 
Ethereal salts, 226 
Ethers, 225 
Ethylene, 108, 109 
Eudiometer, 55 

Fats, 227 
Feldspar, 165, 198 
Fermentation, 217, 219 
Ferric chloride, 202 

oxide, 204 
Ferrous chloride, 203 

hydroxide, 202 

oxide, 202 

sulphate, 203 
Fire-damp, 108 
Flame, 120 
Flame-reactions, 175 
Flour, 236 
Fluorine, 135 
Fluor-spar, 135, 178 
Flux, 200 
Fruit-sugar, 232 
Fusel-oil, 220 

Galenite, 139, 209 
Gallium, 177 
Galvanized iron, 186 
Gas, olefiant, 109 
Gasoline, 107 
German silver, 186 
Glass, 183 
Glauber's salt, 171 
Glucose, 231 
Glucosides, 238, 241 
Gluten, 236 



270 



INDEX. 



Glycerin, 220 
Gold, 215 
Granite, 196 
Grape-sugar, 231 
Graphite, 96 
Gun-cotton, 235 
Gunpowder, 165 
Gypsum, 139, 181 

Heat and chemical change, 4, 30 
Hematite, 199, 204 
Heptane, 107 
Hexane, 107 
Homologous series, 107 
Homology, 107 
Hydrocarbons, 106 
Hydrogen, 45 

dioxide, 65 

preparation, 45 

properties, 48, 49 

sulphide, 142 
Hypothesis, 124 

Illumination, 120 
Incense, 239 
Indigo, 240 
Indium, 177 
Inks, 203 
Iodine, 134 
Iridium, 214 
Iron, 199 

carbonate, 199 

cast, 200 

chlorides, 202 

oxides, 202 

pyrites, 139, 199, 204 

Kaoline, 198 

Kelp, 134 

Kerosene, 107 

Kindling temperature, 29 

Lactose, 234 
Lamp-black, 98 
Lapis lazuli, 198 
Lead, 209 

acetate, 222 

carbonate, 212 

chromate, 207, 211 

oxide, 211 

red oxide, 211 



Lead, sulphate, 139 

sulphide, 209 

white, 212 
Leblanc's method, 172 
Levulose, 232 
Lignite, 100 
Lime, 179 

light, 58 
Limestone, 180 
Litharge, 211 
Lithium, 175 

Magenta, 238 

Magnesia, 185 
Magnesite, 185 
Magnesium, 185 

carbonate, 185 

chloride, 185 

oxide, 185 

sulphate, 185 
Magnetite, 199, 204 
Manganese, 206 

dioxide, 206 

oxides, 206 
Marble, 180 
Marsh-gas, 108 
Marsh's test, 159 
Meerschaum, 185 
Mercuric chloride, 191 
Mercuric oxide, 190 
Mercurous chloride, 190 
Mercury, 190 

chlorides, 190 

oxide, 190 

sulphide, 190 
Metallic properties, 162 
Metals, classification, 161 
Metathesis, 11 
Methane, 107, 108 
Mica, 196 
Minium, 211 
Mixture, mechanical, 9 
Molasses, 232 
Molecular formulas, 126 

weights, 126 
Molecules, 126 
Morphine, 242 
Mortar, 182 
Multiple proportions, 35 

Naphtha, 107 



INDEX. 



271 



Naphthalene. 240 

Narcotine, 242 
Neutralization, 88 
Nickel, 204 
Nicotine, 242 
Nitrates, 73 
Nitric acid, 67, 69 

oxide, 74, 75 
Nitrobenzene, 237 
Nitrocellulose, 235 
Nitrogen, 37 

family, 153 

in air, 20, 39 

oxides, 73 

pentoxide, 74 

peroxide, 74, 76 

trioxide, 74 
Nitroglycerin, 227 
Nitrous acid, 67 

oxide, 74 
Nomenclature, acids, 92 

bases, 93 

salts, 94 

Octane, 107 

Oil of bitter almonds, 238 

Oleo -margarin, 227 

Opium, 242 

Organic chemistry, 216 

Osmium, 214 

Oxides, 30 

Oxygen, 21 

preparation, 21 

properties, 24 
Oxyhydrogen blow-pipe, 58 
Ozone, 64 

in air, 65 

relation to oxygen, 65 

Palladium, 214 
Paper, 235 
Paraffin, 107 
Pattison's process, 191 
Pentane, 107 
Petroleum, 106 
Phenol, 238 
Phosphorite, 153 
Phosphorus, 153 

oxide, 155 

red, 154 
Photography, 194 



Pig iron, 200 

Pitchblende, 208 

Plaster of Paris, 181 

Platinum, 214 
chloride, 214 

Plumbago, 96 

Porcelain, 198 

Potash, 165 

Potassium, 165 

chlorate, 86, 169 
chloride, 86 
chromate, 206 
dichromate, 207 
ferrocyanide, 122 
hydroxide, 167 
hypochlorite, 86 
iodide, 166 
nitrate, 167 

Propane, 107 

Propylene, 108 

Puddling, 201 

Pyroxylin, 234 

Quartz, 159, 160 ' 
Quartzite, 159, 160 
Quinine, 241 

Radicals, 229 

Seduction, 57 
Rbchelle salt, 175 
Rouge, 204 
Eubidium, 177 
Ruby, 197 

Ruby copper, 187, 189 
Rust, 201 

Safety-lamp, 121 
Safety- matches, 154 
Saltpetre, 167 
Salts, 91 

acid, 151 

neutral, 151 

nomenclature, 93 

normal, 151 
Sand, 159 
Saponification, 226 
Sapphire, 197 
Serpentine, 185 
Selenium, 152 
Siderite, 199 
Silica, 159 



272 



INDEX. 



Silicates, 159 
Silicon, 159 

oxide, 160 
Silver, 191 

bromide, 194 

chloride, 194 

iodide, 194 

nitrate, 193 

plating, 192 
Slag, 200 
Slaking, 179 
Slow oxidation, 26 
Soaps, 222 
Soapstone, 185 
Soda, 171 
Sodium, 169 

borate, 173 

carbonate, 171 

chloride, 169 

hydroxide, 170 

hyposulphite, 195 

nitrate, 170 

phosphate, 173 

sulphate, 171 
Solder, 212 
Soldering, 173, 213 
Solution, 7 
Solvay method^ 172 
Spectroscope, 176 
Spirits of wine, 218 
Stalactites, 181 
Stalagmites, 181 
Stannic compounds, 213 
Stannic chloride, 213 
Stannic sulphide, 213 
Stannous compounds, 213 
Stannous chloride, 213 
Starch, 236 
Stearin, 222 
Steel, 201 
Stibine, 159 
Strontium, 183 
Sugar of lead, 222 

milk, 234 
Sugar- refining, 233 
Sulphites, 145 
Sulphur, 139 

dimorphism of, 141 

dioxide, 145 

trioxide, 145 



Sulphuretted hydrogen, 14$ 
Superphosphate of lima 182 
Symbols, 33, 34, 35 

Tannin, 239 
Tanning, 240 
Tellurium, 152 
Tempering, 201 
Thallium, 177 
Theory, 124 
Tin, 212 

dichloride, 213 

oxide, 212 

salt, 213 

sulphide, 213 

tetrachloride, 213 
Tin-stone, 212 
Toluene, 108 
Turkey-red, 241 

Ultramarine, 198 
Uranium, 208 

Valence, 127 
Yerdigris, 222 
Vitriol, blue, 190 

green, 203 

white, 187 

Water, 41 

analysis, 44 
hard, 117, 181, 223 
maximum density. 59 
of crystallization, 41 
as a solvent, 62 
synthesis of, 54, 56 
uses in chemistry, 62 

Water gas, 46, 118 

Water-glass, 174 

Wei don's process, 78 

Wood- spirit, 218 

Wood- vinegar, 221 

Wrought-iron, 200 

Xylene, 108 

Zinc, 186 

blende, 186 
oxide, 186 
sulphate, 187 



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